Duckbill-shaped implantable cardioverter-defibrillator canister and method of use

ABSTRACT

One embodiment of the present invention provides an implantable cardioverter-defibrillator for subcutaneous positioning between the third rib and the twelfth rib within a patient, the implantable cardioverter-defibrillator including a housing; wherein the housing comprises a proximal end having a width and a distal end having a width and wherein the width of the proximal end is less than the width of the distal end; an electrical circuit located within the housing; and an electrode electrically coupled to the electrical circuit and located on the housing.

BACKGROUND OF THE INVENTION

[0001] Defibrillation/cardioversion is a technique employed to counterarrhythmic heart conditions including some tachycardias in the atriaand/or ventricles. Typically, electrodes are employed to stimulate theheart with electrical impulses or shocks, of a magnitude substantiallygreater than pulses used in cardiac pacing.

[0002] Defibrillation/cardioversion systems include body implantableelectrodes and are referred to as implantablecardioverter/defibrillators (ICDs). Such electrodes can be in the formof patches applied directly to epicardial tissue, or at the distal endregions of intravascular catheters, inserted into a selected cardiacchamber. U.S. Pat. Nos. 4,603,705, 4,693,253, 4,944,300, 5,105,810, thedisclosures of which are all incorporated herein by reference, discloseintravascular or transvenous electrodes, employed either alone or incombination with an epicardial patch electrode. Compliant epicardialdefibrillator electrodes are disclosed in U.S. Pat. Nos. 4,567,900 and5,618,287, the disclosures of which are incorporated herein byreference. A sensing epicardial electrode configuration is disclosed inU.S. Pat No. 5,476,503, the disclosure of which is incorporated hereinby reference.

[0003] In addition to epicardial and transvenous electrodes,subcutaneous electrode systems have also been developed. For example,U.S. Pat. Nos. 5,342,407 and 5,603,732, the disclosures of which areincorporated herein by reference, teach the use of a pulsemonitor/generator surgically implanted into the abdomen and subcutaneouselectrodes implanted in the thorax. This system is far more complicatedto use than current ICD systems using transvenous lead systems togetherwith an active can electrode and therefore it has o practical use. Ithas in fact never been used because of the surgical difficulty ofapplying such a device (3 incisions), the impractical abdominal locationof the generator and the electrically poor sensing and defibrillationaspects of such a system.

[0004] Recent efforts to improve the efficiency of ICDs have ledmanufacturers to produce ICDs which are small enough to be implanted inthe pectoral region. In addition, advances in circuit design haveenabled the housing of the ICD to form a subcutaneous electrode. Someexamples of ICDs in which the housing of the ICD serves as an optionaladditional electrode are described in U.S. Pat. Nos. 5,133,353,5,261,400, 5,620,477, and 5,658,321 the disclosures of which areincorporated herein by reference.

[0005] ICDs are now an established therapy for the management of lifethreatening cardiac rhythm disorders, primarily ventricular fibrillation(V-Fib). ICDs are very effective at treating V-Fib, but are therapiesthat still require significant surgery.

[0006] As ICD therapy becomes more prophylactic in nature and used inprogressively less ill individuals, especially children at risk ofcardiac arrest, the requirement of ICD therapy to use intravenouscatheters and transvenous leads is an impediment to very long termmanagement as most individuals will begin to develop complicationsrelated to lead system malfunction sometime in the 5-10 year time frame,often earlier. In addition, chronic transvenous lead systems, theirreimplantation and removals, can damage major cardiovascular venoussystems and the tricuspid valve, as well as result in life threateningperforations of the great vessels and heart. Consequently, use oftransvenous lead systems, despite their many advantages, are not withouttheir chronic patient management limitations in those with lifeexpectancies of >5 years. The problem of lead complications is evengreater in children where body growth can substantially altertransvenous lead function and lead to additional cardiovascular problemsand revisions. Moreover, transvenous ICD systems also increase cost andrequire specialized interventional rooms and equipment as well asspecial skill for insertion. These systems are typically implanted bycardiac electrophysiologists who have had a great deal of extratraining.

[0007] In addition to the background related to ICD therapy, the presentinvention requires a brief understanding of automatic externaldefibrillator (AED) therapy. AEDs employ the use of cutaneous patchelectrodes to effect defibrillation under the direction of a bystanderuser who treats the patient suffering from V-Fib. AEDs can be aseffective as an ICD if applied to the victim promptly within 2 to 3minutes.

[0008] AED therapy has great appeal as a tool for diminishing the riskof death in public venues such as in air flight. However, an AED must beused by another individual, not the person suffering from the potentialfatal rhythm. It is more of a public health tool than a patient-specifictool like an ICD. Because >75% of cardiac arrests occur in the home, andover half occur in the bedroom, patients at risk of cardiac arrest areoften alone or asleep and can not be helped in time with an AED.Moreover, its success depends to a reasonable degree on an acceptablelevel of skill and calm by the bystander user.

[0009] What is needed therefore, especially for children and forprophylactic long term use, is a combination of the two forms of therapywhich would provide prompt and near-certain defibrillation, like an ICD,but without the long-term adverse sequelae of a transvenous lead systemwhile simultaneously using most of the simpler and lower cost technologyof an AED. What is also needed is a cardioverter/defibrillator that isof simple design and can be comfortably implanted in a patient for manyyears.

SUMMARY OF THE INVENTION

[0010] One embodiment of the present invention provides an implantablecardioverter-defibrillator for subcutaneous positioning between thethird rib and the twelfth rib within a patient, the implantablecardioverter-defibrillator including a housing; wherein the housingcomprises a proximal end having a width and a distal end having a widthand wherein the width of the proximal end is less than the width of thedistal end; an electrical circuit located within the housing; and anelectrode electrically coupled to the electrical circuit and located onthe housing.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] For a better understanding of the invention, reference is nowmade to the drawings where like numerals represent similar objectsthroughout the figures where:

[0012]FIG. 1 is a schematic view of a Subcutaneous ICD (S-ICD) of thepresent invention;

[0013]FIG. 2 is a schematic view of an alternate embodiment of asubcutaneous electrode of the present invention;

[0014]FIG. 3 is a schematic view of an alternate embodiment of asubcutaneous electrode of the present invention;

[0015]FIG. 4 is a schematic view of the S-ICD and lead of FIG. 1subcutaneously implanted in the thorax of a patient;

[0016]FIG. 5 is a schematic view of the S-ICD and lead of FIG. 2subcutaneously implanted in an alternate location within the thorax of apatient;

[0017]FIG. 6 is a schematic view of the S-ICD and lead of FIG. 3subcutaneously implanted in the thorax of a patient;

[0018]FIG. 7 is a schematic view of the method of making a subcutaneouspath from the preferred incision and housing implantation point to atermination point for locating a subcutaneous electrode of the presentinvention;

[0019]FIG. 8 is a schematic view of an introducer set for performing themethod of lead insertion of any of the described embodiments;

[0020]FIG. 9 is a schematic view of an alternative S-ICD of the presentinvention illustrating a lead subcutaneously and serpiginously implantedin the thorax of a patient for use particularly in children;

[0021]FIG. 10 is a schematic view of an alternate embodiment of an S-ICDof the present invention;

[0022]FIG. 11 is a schematic view of the S-ICD of FIG. 10 subcutaneouslyimplanted in the thorax of a patient;

[0023]FIG. 12 is a schematic view of yet a further embodiment where thecanister of the S-ICD of the present invention is shaped to beparticularly useful in placing subcutaneously adjacent and parallel to arib of a patient; and

[0024]FIG. 13 is a schematic of a different embodiment where thecanister of the S-ICD of the present invention is shaped to beparticularly useful in placing subcutaneously adjacent and parallel to arib of a patient.

[0025]FIG. 14 is a schematic view of a Unitary Subcutaneous ICD (US-ICD)of the present invention;

[0026]FIG. 15 is a schematic view of the US-ICD subcutaneously implantedin the thorax of a patient;

[0027]FIG. 16 is a schematic view of the method of making a subcutaneouspath from the preferred incision for implanting the US-ICD.

[0028]FIG. 17 is a schematic view of an introducer for performing themethod of US-ICD implantation; and

[0029]FIG. 18 is an exploded schematic view of an alternate embodimentof the present invention with a plug-in portion that containsoperational circuitry and means for generatingcardioversion/defibrillation shock waves.

[0030]FIG. 19 is a top perspective view of an alternative S-ICD canisterof the present invention depicting the top side of the canister housingand a lead electrode coupled to the S-ICD canister;

[0031]FIG. 20 is an exploded bottom perspective view of the S-ICDcanister of FIG. 19 showing an electrode in the shape of a thumbnailpositioned on the bottom surface of the canister housing;

[0032]FIG. 21 is a front elevational view of the S-ICD canister of FIG.19 depicting the curved canister housing;

[0033]FIG. 22 is a partial schematic view of the S-ICD canister of thepresent invention implanted subcutaneously in the thorax of therecipient patient;

[0034]FIG. 23A is a top plan view of an alternative S-ICD canister ofthe present invention having a duckbill-shaped end to the canisterhousing at the proximal end;

[0035]FIG. 23B is a top plan view of an alternative S-ICD canister ofthe present invention having a duckbill-shaped canister housing with analternative proximal head configuration;

[0036]FIG. 24A is a top plan view of an alternative S-ICD canister ofthe present invention having a rectangular-shaped canister housing;

[0037]FIG. 24B is a top plan view of an alternative S-ICD canister ofthe present invention having a square-shaped canister housing with atriangular shaped electrode;

[0038]FIG. 24C is a top plan view of an alternative S-ICD canister ofthe present invention having a square-shaped canister housing with asquare shaped electrode;

[0039]FIG. 25A is a top plan view of an alternative S-ICD canister ofthe present invention having a tongue depressor-shaped canister housing;

[0040]FIG. 25B is a top plan view of an alternative S-ICD canister ofthe present invention having a modified tongue depressor-shaped canisterhousing;

[0041]FIG. 26A is a top plan view of an alternative S-ICD canister ofthe present invention having a multi-segment canister housing;

[0042]FIG. 26B is a front elevational view of the S-ICD canister of FIG.26A depicting the curved proximal segment and the planar distal segmentof the multi-segment canister housing; and

[0043]FIG. 26C is a front elevational view of the S-ICD canister of FIG.26A depicting the curved proximal segment and the curved distal segmentof the multi-segment canister housing.

DETAILED DESCRIPTION OF THE INVENTION

[0044] Turning now to FIG. 1, the S-ICD of the present invention isillustrated. The S-ICD consists of an electrically active canister 11and a subcutaneous electrode 13 attached to the canister. The canisterhas an electrically active surface 15 that is electrically insulatedfrom the electrode connector block 17 and the canister housing 16 viainsulating area 14. The canister can be similar to numerous electricallyactive canisters commercially available in that the canister willcontain a battery supply, capacitor and operational circuitry.Alternatively, the canister can be thin and elongated to conform to theintercostal space. The circuitry will be able to monitor cardiac rhythmsfor tachycardia and fibrillation, and if detected, will initiatecharging the capacitor and then delivering cardioversion /defibrillationenergy through the active surface of the housing and to the subcutaneouselectrode. Examples of such circuitry are described in U.S. Pat. Nos.4,693,253 and 5,105,810, the entire disclosures of which are hereinincorporated by reference. The canister circuitry can providecardioversion/ defibrillation energy in different types of waveforms. Inthe preferred embodiment, a 100 μF biphasic waveform is used ofapproximately 10-20 ms total duration and with the initial phasecontaining approximately ⅔ of the energy, however, any type of waveformcan be utilized such as monophasic, biphasic, multiphasic or alternativewaveforms as is known in the art.

[0045] In addition to providing cardioversion/ defibrillation energy,the circuitry can also provide transthoracic cardiac pacing energy. Theoptional circuitry will be able to monitor the heart for bradycardiaand/or tachycardia rhythms. Once a bradycardia or tachycardia rhythm isdetected, the circuitry can then deliver appropriate pacing energy atappropriate intervals through the active surface and the subcutaneouselectrode. Pacing stimuli will be biphasic in the preferred embodimentand similar in pulse amplitude to that used for conventionaltransthoracic pacing.

[0046] This same circuitry can also be used to deliver low amplitudeshocks on the T-wave for induction of ventricular fibrillation fortesting S-ICD performance in treating V-Fib as is described in U.S. Pat.No. 5,129,392, the entire disclosure of which is hereby incorporated byreference. Also the circuitry can be provided with rapid induction ofventricular fibrillation or ventricular tachycardia using rapidventricular pacing. Another optional way for inducing ventricularfibrillation would be to provide a continuous low voltage, i.e., about 3volts, across the heart during the entire cardiac cycle.

[0047] Another optional aspect of the present invention is that theoperational circuitry can detect the presence of atrial fibrillation asdescribed in Olson, W. et al. “Onset And Stability For VentricularTachyarrhythmia Detection in an Implantable Cardioverter andDefibrillator,” Computers in Cardiology (1986) pp. 167-170. Detectioncan be provided via R-R Cycle length instability detection algorithms.Once atrial fibrillation has been detected, the operational circuitrywill then provide QRS synchronized atrial defibrillation/cardioversionusing the same shock energy and waveshape characteristics used forventricular defibrillation/cardioversion.

[0048] The sensing circuitry will utilize the electronic signalsgenerated from the heart and will primarily detect QRS waves. In oneembodiment, the circuitry will be programmed to detect only ventriculartachycardias or fibrillations. The detection circuitry will utilize inits most direct form, a rate detection algorithm that triggers chargingof the capacitor once the ventricular rate exceeds some predeterminedlevel for a fixed period of time: for example, if the ventricular rateexceeds 240 bpm on average for more than 4 seconds. Once the capacitoris charged, a confirmatory rhythm check would ensure that the ratepersists for at least another 1 second before discharge. Similarly,termination algorithms could be instituted that ensure that a rhythmless than 240 bpm persisting for at least 4 seconds before the capacitorcharge is drained to an internal resistor. Detection, confirmation andtermination algorithms as are described above and in the art can bemodulated to increase sensitivity and specificity by examining QRSbeat-to-beat uniformity, QRS signal frequency content, R-R intervalstability data, and signal amplitude characteristics all or part ofwhich can be used to increase or decrease both sensitivity andspecificity of S-ICD arrhythmia detection function.

[0049] In addition to use of the sense circuitry for detection of V-Fibor V-Tach by examining the QRS waves, the sense circuitry can check forthe presence or the absence of respiration. The respiration rate can bedetected by monitoring the impedance across the thorax usingsubthreshold currents delivered across the active can and the highvoltage subcutaneous lead electrode and monitoring the frequency inundulation in the waveform that results from the undulations oftransthoracic impedance during the respiratory cycle. If there is noundulation, then the patent is not respiring and this lack ofrespiration can be used to confirm the QRS findings of cardiac arrest.The same technique can be used to provide information about therespiratory rate or estimate cardiac output as described in U.S. Pat.Nos. 6,095,987, 5,423,326, 4,450,527, the entire disclosures of whichare incorporated herein by reference

[0050] The canister of the present invention can be made out of titaniumalloy or other presently preferred electrically active canister designs.However, it is contemplated that a malleable canister that can conformto the curvature of the patient's chest will be preferred. In this waythe patient can have a comfortable canister that conforms to the shapeof the patient's rib cage. Examples of conforming canisters are providedin U.S. Pat. No. 5,645,586, the entire disclosure of which is hereinincorporated by reference. Therefore, the canister can be made out ofnumerous materials such as medical grade plastics, metals, and alloys.In the preferred embodiment, the canister is smaller than 60 cc volumehaving a weight of less than 100 gms for long term wearability,especially in children. The canister and the lead of the S-ICD can alsouse fractal or wrinkled surfaces to increase surface area to improvedefibrillation capability. Because of the primary prevention role of thetherapy and the likely need to reach energies over 40 Joules, a featureof the preferred embodiment is that the charge time for the therapy,intentionally e relatively long to allow capacitor charging within thelimitations of device size. Examples of small ICD housings are disclosedin U.S. Pat. Nos. 5,597,956 and 5,405,363, the entire disclosures ofwhich are herein incorporated by reference.

[0051] Different subcutaneous electrodes 13 of the present invention areillustrated in FIGS. 1-3. Turning to FIG. 1, the lead 21 for thesubcutaneous electrode is preferably composed of silicone orpolyurethane insulation. The electrode is connected to the canister atits proximal end via connection port 19 which is located on anelectrically insulated area 17 of the canister. The electrodeillustrated is a composite electrode with three different electrodesattached to the lead. In the embodiment illustrated, an optional anchorsegment 52 is attached at the most distal end of the subcutaneouselectrode for anchoring the electrode into soft tissue such that theelectrode does not dislodge after implantation.

[0052] The most distal electrode on the composite subcutaneous electrodeis a coil electrode 27 that is used for delivering the high voltagecardioversion/ defibrillation energy across the heart. The coilcardioversion/defibrillation electrode is about 5-10 cm in length.Proximal to the coil electrode are two sense electrodes, a first senseelectrode 25 is located proximally to the coil electrode and a secondsense electrode 23 is located proximally to the first sense electrode.The sense electrodes are spaced far enough apart to be able to have goodQRS detection. This spacing can range from 1 to 10 cm with 4 cm beingpresently preferred. The electrodes may or may not be circumferentialwith the preferred embodiment. Having the electrodes non-circumferentialand positioned outward, toward the skin surface, is a means to minimizemuscle artifact and enhance QRS signal quality. The sensing electrodesare electrically isolated from the cardioversion/defibrillationelectrode via insulating areas 29. Similar types ofcardioversion/defibrillation electrodes are currently commerciallyavailable in a transvenous configuration. For example, U.S. Pat. No.5,534,022, the entire disclosure of which is herein incorporated byreference, disclosures a composite electrode with a coilcardioversion/defibrillation electrode and sense electrodes.Modifications to this arrangement is contemplated within the scope ofthe invention. One such modification is illustrated in FIG. 2 where thetwo sensing electrodes 25 and 23 are non-circumferential sensingelectrodes and one is located at the distal end, the other is locatedproximal thereto with the coil electrode located in between the twosensing electrodes. In this embodiment the sense electrodes are spacedabout 6 to about 12 cm apart depending on the length of the coilelectrode used. FIG. 3 illustrates yet a further embodiment where thetwo sensing electrodes are located at the distal end to the compositeelectrode with the coil electrode located proximally thereto. Otherpossibilities exist and are contemplated within the present invention.For example, having only one sensing electrode, either proximal ordistal to the coil cardioversion/defibrillation electrode with the coilserving as both a sensing electrode and a cardioversion/defibrillationelectrode.

[0053] It is also contemplated within the scope of the invention thatthe sensing of QRS waves (and transthoracic impedance) can be carriedout via sense electrodes on the canister housing or in combination withthe cardioversion/defibrillation coil electrode and/or the subcutaneouslead sensing electrode(s). In this way, sensing could be performed viathe one coil electrode located on the subcutaneous electrode and theactive surface on the canister housing. Another possibility would be tohave only one sense electrode located on the subcutaneous electrode andthe sensing would be performed by that one electrode and either the coilelectrode on the subcutaneous electrode or by the active surface of thecanister. The use of sensing electrodes on the canister would eliminatethe need for sensing electrodes on the subcutaneous electrode. It isalso contemplated that the subcutaneous electrode would be provided withat least one sense electrode, the canister with at least one senseelectrode, and if multiple sense electrodes are used on either thesubcutaneous electrode and/or the canister, that the best QRS wavedetection combination will be identified when the S-ICD is implanted andthis combination can be selected, activating the best sensingarrangement from all the existing sensing possibilities. Turning againto FIG. 2, two sensing electrodes 26 and 28 are located on theelectrically active surface 15 with electrical insulator rings 30 placedbetween the sense electrodes and the active surface. These canistersense electrodes could be switched off and electrically insulated duringand shortly after defibrillation/ cardioversion shock delivery. Thecanister sense electrodes may also be placed on the electricallyinactive surface of the canister. In the embodiment of FIG. 2, there areactually four sensing electrodes, two on the subcutaneous lead and twoon the canister. In the preferred embodiment, the ability to changewhich electrodes are used for sensing would be a programmable feature ofthe S-ICD to adapt to changes in the patient physiology and size (in thecase of children) over time. The programming could be done via the useof physical switches on the canister, or as presently preferred, via theuse of a programming wand or via a wireless connection to program thecircuitry within the canister.

[0054] The canister could be employed as either a cathode or an anode ofthe S-ICD cardioversion/defibrillation system. If the canister is thecathode, then the subcutaneous coil electrode would be the anode.Likewise, if the canister is the anode, then the subcutaneous electrodewould be the cathode.

[0055] The active canister housing will provide energy and voltageintermediate to that available with ICDs and most AEDS. The typicalmaximum voltage necessary for ICDs using most biphasic waveforms isapproximately 750 Volts with an associated maximum energy ofapproximately 40 Joules. The typical maximum voltage necessary for AEDsis approximately 2000-5000 Volts with an associated maximum energy ofapproximately 200-360 Joules depending upon the model and waveform used.The S-ICD of the present invention uses maximum voltages in the range ofabout 700 to about 3150 Volts and is associated with energies of about40 to about 210 Joules. The capacitance of the S-ICD could range fromabout 50 to about 200 micro farads.

[0056] The sense circuitry contained within the canister is highlysensitive and specific for the presence or absence of life threateningventricular arrhythmias. Features of the detection algorithm areprogrammable and the algorithm is focused on the detection of V-FIB andhigh rate V-TACH (>240 bpm). Although the S-ICD of the present inventionmay rarely be used for an actual life threatening event, the simplicityof design and implementation allows it to be employed in largepopulations of patients at modest risk with modest cost by non-cardiacelectrophysiologists. Consequently, the S-ICD of the present inventionfocuses mostly on the detection and therapy of the most malignant rhythmdisorders. As part of the detection algorithm's applicability tochildren, the upper rate range is programmable upward for use inchildren, known to have rapid supraventricular tachycardias and morerapid ventricular fibrillation. Energy levels also are programmabledownward in order to allow treatment of neonates and infants.

[0057] Turning now to FIG. 4, the optimal subcutaneous placement of theS-ICD of the present invention is illustrated. As would be evidence to aperson skilled in the art, the actual location of the S-ICD is in asubcutaneous space that is developed during the implantation process.The heart is not exposed during this process and the heart isschematically illustrated in the figures only for help in understandingwhere the canister and coil electrode are three dimensionally located inthe left mid-clavicular line approximately at the level of theinframammary crease at approximately the 5th rib. The lead 21 of thesubcutaneous electrode traverses in a subcutaneous path around thethorax terminating with its distal electrode end at the posterioraxillary line ideally just lateral to the left scapula. This way thecanister and subcutaneous cardioversion/defibrillation electrode providea reasonably good pathway for current delivery to the majority of theventricular myocardium.

[0058]FIG. 5 illustrates a different placement of the present invention.The S-ICD canister with the active housing is located in the leftposterior axillary line approximately lateral to the tip of the inferiorportion of the scapula. This location is especially useful in children.The lead 21 of the subcutaneous electrode traverses in a subcutaneouspath around the thorax terminating with its distal electrode end at theanterior precordial region, ideally in the inframammary crease. FIG. 6illustrates the embodiment of FIG. 1 subcutaneously implanted in thethorax with the proximal sense electrodes 23 and 25 located atapproximately the left axillary line with thecardioversion/defibrillation electrode just lateral to the tip of theinferior portion of the scapula.

[0059]FIG. 7 schematically illustrates the method for implanting theS-ICD of the present invention. An incision 31 is made in the leftanterior axillary line approximately at the level of the cardiac apex.This incision location is distinct from that chosen for S-ICD placementand is selected specifically to allow both canister location moremedially in the left inframammary crease and lead positioning moreposteriorly via the introducer set (described below) around to the leftposterior axillary line lateral to the left scapula. That said, theincision can be anywhere on the thorax deemed reasonably by theimplanting physician although in the preferred embodiment, the S-ICD ofthe present invention will be applied in this region. A subcutaneouspathway 33 is then created medially to the inframmary crease for thecanister and posteriorly to the left posterior axillary line lateral tothe left scapula for the lead.

[0060] The S-ICD canister 11 is then placed subcutaneously at thelocation of the incision or medially at the subcutaneous region at theleft inframmary crease. The subcutaneous electrode 13 is placed with aspecially designed curved introducer set 40 (see FIG. 8). The introducerset comprises a curved trocar 42 and a stiff curved peel away sheath 44.The peel away sheath is curved to allow for placement around the ribcage of the patient in the subcutaneous space created by the trocar. Thesheath has to be stiff enough to allow for the placement of theelectrodes without the sheath collapsing or bending. Preferably thesheath is made out of a biocompatible plastic material and is perforatedalong its axial length to allow for it to split apart into two sections.The trocar has a proximal handle 41 and a curved shaft 43. The distalend 45 of the trocar is tapered to allow for dissection of asubcutaneous path 33 in the patient. Preferably, the trocar iscannulated having a central Lumen 46 and terminating in an opening 48 atthe distal end. Local anesthetic such as lidocaine can be delivered, ifnecessary, through the lumen or through a curved and elongated needledesigned to anesthetize the path to be used for trocar insertion shouldgeneral anesthesia not be employed. The curved peel away sheath 44 has aproximal pull tab 49 for breaking the sheath into two halves along itsaxial shaft 47. The sheath is placed over a guidewire inserted throughthe trocar after the subcutaneous path has been created. Thesubcutaneous pathway is then developed until it terminatessubcutaneously at a location that, if a straight line were drawn fromthe canister location to the path termination point the line wouldintersect a substantial portion of the left ventricular mass of thepatient. The guidewire is then removed leaving the peel away sheath. Thesubcutaneous lead system is then inserted through the sheath until it isin the proper location. Once the subcutaneous lead system is in theproper location, the sheath is split in half using the pull tab 49 andremoved. If more than one subcutaneous electrode is being used, a newcurved peel away sheath can be used for each subcutaneous electrode.

[0061] The S-ICD will have prophylactic use in adults where chronictransvenous/epicardial ICD lead systems pose excessive risk or havealready resulted in difficulty, such as sepsis or lead fractures. It isalso contemplated that a major use of the S-ICD system of the presentinvention will be for prophylactic use in children who are at risk forhaving fatal arrhythmias, where chronic transvenous lead systems posesignificant management problems. Additionally, with the use of standardtransvenous ICDs in children, problems develop during patient growth inthat the lead system does not accommodate the growth. FIG. 9 illustratesthe placement of the S-ICD subcutaneous lead system such that he problemthat growth presents to the lead system is overcome. The distal end ofthe subcutaneous electrode is placed in the same location as describedabove providing a good location for the coilcardioversion/defibrillation electrode 27 and the sensing electrodes 23and 25. The insulated lead 21, however is no longer placed in a taughtconfiguration. Instead, the lead is serpiginously placed with aspecially designed introducer trocar and sheath such that it hasnumerous waves or bends. As the child grows, the waves or bends willstraighten out lengthening the lead system while maintaining properelectrode placement. Although it is expected that fibrous scarringespecially around the defibrillation coil will help anchor it intoposition to maintain its posterior position during growth, a lead systemwith a distal tine or screw electrode anchoring system 52 can also beincorporated into the distal tip of the lead to facilitate leadstability (see FIG. 1). Other anchoring systems can also be used such ashooks, sutures, or the like.

[0062]FIGS. 10 and 11 illustrate another embodiment of the present S-ICDinvention. In this embodiment there are two subcutaneous electrodes 13and 13′ of opposite polarity to the canister. The additionalsubcutaneous electrode 13′ is essentially identical to the previouslydescribed electrode In this embodiment the cardioversion/defibrillationenergy is delivered between the active surface of the canister and thetwo coil electrodes 27 and 27′. Additionally, provided in the canisteris means for selecting the optimum sensing arrangement between the foursense electrodes 23, 23′, 25, and 25′. The two electrodes aresubcutaneously placed on the same side of the heart. As illustrated inFIG. 6, one subcutaneous electrode 13 is placed inferiorly and the otherelectrode 13′ is placed superiorly. It is also contemplated with thisdual subcutaneous electrode system that the canister and onesubcutaneous electrode are the same polarity and the other subcutaneouselectrode is the opposite polarity.

[0063] Turning now to FIGS. 12 and 13, further embodiments areillustrated where the canister 11 of the S-ICD of the present inventionis shaped to be particularly useful in placing subcutaneously adjacentand parallel to a rib of a patient. The canister is long, thin, andcurved to conform to the shape of the patient's rib. In the embodimentillustrated in FIG. 12, the canister has a diameter ranging from about0.5 cm to about 2 cm without 1 cm being presently preferred.Alternatively, instead of having a circular cross sectional area, thecanister could have a rectangular or square cross sectional area asillustrated in FIG. 13 without falling outside of the scope of thepresent invention. The length of the canister can vary depending on thesize of the patient's thorax. Currently the canister is about 5 cm toabout 15 cm long with about 10 being presently preferred. The canisteris curved to conform to the curvature of the ribs of the thorax. Theradius of the curvature will vary depending on the size of the patient,with smaller radiuses for smaller patients and larger radiuses forlarger patients. The radius of the curvature can range from about 5 cmto about 35 cm depending on the size of the patient. Additionally, theradius of the curvature need not be uniform throughout the canister suchthat it can be shaped closer to the shape of the ribs. The canister hasan active surface, 15 that is located on the interior (concave) portionof the curvature and an inactive surface 16 that is located on theexterior (convex) portion of the curvature. The leads of theseembodiments, which are not illustrated except for the attachment port 19and the proximal end of the lead 21, can be any of the leads previouslydescribed above, with the lead illustrated in FIG. 1 being presentlypreferred.

[0064] The circuitry of this canister is similar to the circuitrydescribed above. Additionally, the canister can optionally have at leastone sense electrode located on either the active surface of the inactivesurface and the circuitry within the canister can be programmable asdescribed above to allow for the selection of the best sense electrodes.It is presently preferred that the canister have two sense electrodes 26and 28 located on the inactive surface of the canisters as illustrated,where the electrodes are spaced from about 1 to about 10 cm apart with aspacing of about 3 cm being presently preferred. However, the senseelectrodes can be located on the active surface as described above.

[0065] It is envisioned that the embodiment of FIG. 12 will besubcutaneously implanted adjacent and parallel to the left anterior 5thrib, either between the 4th and 5th ribs or between the 5th and 6thribs. However other locations can be used.

[0066] Another component of the S-ICD of the present invention is acutaneous test electrode system designed to simulate the subcutaneoushigh voltage shock electrode system as well as the QRS cardiac rhythmdetection system. This test electrode system is comprised of a cutaneouspatch electrode of similar surface area and impedance to that of theS-ICD canister itself together with a cutaneous strip electrodecomprising a defibrillation strip as well as two button electrodes forsensing of the QRS. Several cutaneous strip electrodes are available toallow for testing various bipole spacings to optimize signal detectioncomparable to the implantable system.

[0067] FIGS. 14 to 18 depict particular US-ICD embodiments of thepresent invention. The various sensing, shocking and pacing circuitry,described in detail above with respect to the S-ICD embodiments, mayadditionally be incorporated into the following US-ICD embodiments.Furthermore, particular aspects of any individual S-ICD embodimentdiscussed above, may be incorporated, in whole or in part, into theUS-ICD embodiments depicted in the following figures.

[0068] Turning now to FIG. 14, the US-ICD of the present invention isillustrated. The US-ICD consists of a curved housing 1211 with a firstand second end. The first end 1413 is thicker than the second end 1215.This thicker area houses a battery supply, capacitor and operationalcircuitry for the US-ICD. The circuitry will be able to monitor cardiacrhythms for tachycardia and fibrillation, and if detected, will initiatecharging the capacitor and then delivering cardioversion/defibrillationenergy through the two cardioversion/defibrillating electrodes 1417 and1219 located on the outer surface of the two ends of the housing. Thecircuitry can provide cardioversion/defibrillation energy in differenttypes of waveforms. In the preferred embodiment, a 100 μF biphasicwaveform is used of approximately 10-20 ms total duration and with theinitial phase containing approximately ⅔ of the energy, however, anytype of waveform can be utilized such as monophasic, biphasic,multiphasic or alternative waveforms as is known in the art.

[0069] The housing of the present invention can be made out of titaniumalloy or other presently preferred ICD designs. It is contemplated thatthe housing is also made out of biocompatible plastic materials thatelectronically insulate the electrodes from each other. However, it iscontemplated that a malleable canister that can conform to the curvatureof the patient's chest will be preferred. In this way the patient canhave a comfortable canister that conforms to the unique shape of thepatient's rib cage. Examples of conforming ICD housings are provided inU.S. Pat. No. 5,645,586, the entire disclosure of which is hereinincorporated by reference. In the preferred embodiment, the housing iscurved in the shape of a 5th rib of a person. Because there are manydifferent sizes of people, the housing will come in differentincremental sizes to allow a good match between the size of the rib cageand the size of the US-ICD. The length of the US-ICD will range fromabout 15 to about 50 cm. Because of the primary preventative role of thetherapy and the need to reach energies over 40 Joules, a feature of thepreferred embodiment is that the charge time for the therapy,intentionally be relatively long to allow capacitor charging within thelimitations of device size.

[0070] The thick end of the housing is currently needed to allow for theplacement of the battery supply, operational circuitry, and capacitors.It is contemplated that the thick end will be about 0.5 cm to about 2 cmwide with about 1 cm being presently preferred. As microtechnologyadvances, the thickness of the housing will become smaller.

[0071] The two cardioversion/defibrillation electrodes on the housingare used for delivering the high voltage cardioversion/defibrillationenergy across the heart. In the preferred embodiment, thecardioversion/defibrillation electrodes are coil electrodes, however,other cardioversion/defibrillation electrodes could be used such ashaving electrically isolated active surfaces or platinum alloyelectrodes. The coil cardioversion/defibrillation electrodes are about5-10 cm in length. Located on the housing between the twocardioversion/defibrillation electrodes are two sense electrodes 1425and 1427. The sense electrodes are spaced far enough apart to be able tohave good QRS detection. This spacing can range from 1 to 10 cm with 4cm being presently preferred. The electrodes may or may not becircumferential with the preferred embodiment. Having the electrodesnon-circumferential and positioned outward, toward the skin surface, isa means to minimize muscle artifact and enhance QRS signal quality. Thesensing electrodes are electrically isolated from thecardioversion/defibrillation electrode via insulating areas 1423.Analogous types of cardioversion/defibrillation electrodes are currentlycommercially available in a transvenous configuration. For example, U.S.Pat. No. 5,534,022, the entire disclosure of which is hereinincorporated by reference, discloses a composite electrode with a coilcardioversion/defibrillation electrode and sense electrodes.Modifications to this arrangement is contemplated within the scope ofthe invention. One such modification is to have the sense electrodes atthe two ends of the housing and have the cardioversion/defibrillationelectrodes located in between the sense electrodes. Another modificationis to have three or more sense electrodes spaced throughout the housingand allow for the selection of the two best sensing electrodes. If threeor more sensing electrodes are used, then the ability to change whichelectrodes are used for sensing would be a programmable feature of theUS-ICD to adapt to changes in the patient physiology and size over time.The programming could be done via the use of physical switches on thecanister, or as presently preferred, via the use of a programming wandor via a wireless connection to program the circuitry within thecanister.

[0072] Turning now to FIG. 15, the optimal subcutaneous placement of theUS-ICD of the present invention is illustrated. As would be evident to aperson skilled in the art, the actual location of the US-ICD is in asubcutaneous space that is developed during the implantation process.The heart is not exposed during this process and the heart isschematically illustrated in the figures only for help in understandingwhere the device and its various electrodes are three dimensionallylocated in the thorax of the patient. The US-ICD is located between theleft mid-clavicular line approximately at the level of the inframammarycrease at approximately the 5th rib and the posterior axillary line,ideally just lateral to the left scapula. This way the US-ICD provides areasonably good pathway for current delivery to the majority of theventricular myocardium.

[0073]FIG. 16 schematically illustrates the method for implanting theUS-ICD of the present invention. An incision 1631 is made in the leftanterior axillary line approximately at the level of the cardiac apex. Asubcutaneous pathway is then created that extends posteriorly to allowplacement of the US-ICD. The incision can be anywhere on the thoraxdeemed reasonable by the implanting physician although in the preferredembodiment, the US-ICD of the present invention will be applied in thisregion. The subcutaneous pathway is created medially to the inframammarycrease and extends posteriorly to the left posterior axillary line. Thepathway is developed with a specially designed curved introducer 1742(see FIG. 17). The trocar has a proximal handle 1641 and a curved shaft1643. The distal end 1745 of the trocar is tapered to allow fordissection of a subcutaneous path in the patient. Preferably, the trocaris cannulated having a central lumen 1746 and terminating in an opening1748 at the distal end. Local anesthetic such as lidocaine can bedelivered, if necessary, through the lumen or through a curved andelongated needle designed to anesthetize the path to be used for trocarinsertion should general anesthesia not be employed. Once thesubcutaneous pathway is developed, the US-ICD is implanted in thesubcutaneous space, the skin incision is closed using standardtechniques.

[0074] As described previously, the US-ICDs of the present inventionvary in length and curvature. The US-ICDs are provided in incrementalsizes for subcutaneous implantation in different sized patients. Turningnow to FIG. 18, a different embodiment is schematically illustrated inexploded view which provides different sized US-ICDs that are easier tomanufacture. The different sized US-ICDs will all have the same sizedand shaped thick end 1413. The thick end is hollow inside allowing forthe insertion of a core operational member 1853. The core membercomprises a housing 1857 which contains the battery supply, capacitorand operational circuitry for the US-ICD. The proximal end of the coremember has a plurality of electronic plug connectors. Plug connectors1861 and 1863 are electronically connected to the sense electrodes viapressure fit connectors (not illustrated) inside the thick end which arestandard in the art. Plug connectors 1865 and 1867 are alsoelectronically connected to the cardioverter/defibrillator electrodesvia pressure fit connectors inside the thick end. The distal end of thecore member comprises an end cap 1855, and a ribbed fitting 1859 whichcreates a water-tight seal when the core member is inserted into opening1851 of the thick end of the US-ICD.

[0075] The core member of the different sized and shaped US-ICD will allbe the same size and shape. That way, during an implantation procedures,multiple sized US-ICDs can be available for implantation, each onewithout a core member. Once the implantation procedure is beingperformed, then the correct sized US-ICD can be selected and the coremember can be inserted into the US-ICD and then programmed as describedabove. Another advantage of this configuration is when the batterywithin the core member needs replacing it can be done without removingthe entire US-ICD.

[0076] FIGS. 19-2G refer generally to alternative S-ICD/US-ICD canisterembodiments. Although the following canister designs, various materialconstructions, dimensions and curvatures, discussed in detail below, maybe incorporated into either S-ICD or US-ICD canister embodiments,hereinafter, these attributes will be discussed solely with respect toS-ICDs.

[0077] The canisters illustrated in these Figures possess aconfiguration that may 1) aid in the initial canister implantation; 2)restrict canister displacement once properly positioned; 3) create aconsistently focused array of energy delivered toward the recipient'sheart with less disbursement to other areas of the thorax; 4) allow forgood signal reception from the heart by an S-ICD system; or 5) providesignificant comfort and long-term wearability in a broad spectrum ofpatients with differing thoracic sizes and shapes. More particularly,FIGS. 19-26 detail various material constructions, dimensions andcurvatures that are incorporated within the numerous S-ICD canisterdesigns detailed in FIGS. 19-26C.

[0078] Referring now to the particular embodiments, FIG. 19 depicts anS-ICD canister 190 of an embodiment of the present invention. The shellof the S-ICD canister 190 comprises a hermetically sealed housing 192that encases the electronics for the S-ICD canister 190. As with thepreviously described S-ICD devices, the electronics of the presentembodiment include, at a minimum, a battery supply, a capacitor andoperational circuitry. FIG. 19 further depicts a lead electrode 191coupled to the shell of the canister through a lead 193. A dorsal fin197 may be disposed on the lead electrode 191 to facilitate thepositioning of the lead electrode.

[0079] The S-ICD devices of the present invention provide an energy(electric field strength (V/cm), current density (A/cm²), voltagegradient (V/cm) or other measured unit of energy) to a patient's heart.S-ICD devices of the present invention will generally use voltages inthe range of 700 V to 3150 V, requiring energies of approximately 40 Jto 210 J. These energy requirements will vary, however, depending uponthe form of treatment, the proximity of the canister from the patient'sheart, the relative relationship of the S-ICD canister's electrode tothe lead electrode, the nature of the patient's underlying heartdisease, the specific cardiac disorder being treated, and the ability toovercome diversion of the S-ICD electrical output into other thoracictissues.

[0080] Ideally, the emitted energy from the S- ICD device will bedirected into the patient's anterior mediastinum, through the majorityof the heart, and out to the coupled lead electrode positioned in theposterior, posterolateral and/or lateral thoracic locations.Furthermore, it is desirable that the S-ICD canister 190 be capable ofdelivering this directed energy, as a general rule, at an adequateeffective field strength of about 3-5 V/cm to approximately 90 percentof a patient's ventricular myocardium using a biphasic waveform. Thisdelivered effective field strength should be adequate for defibrillationof the patient's heart—an intended application of an embodiment of thepresent invention.

[0081] Increased energy requirements necessitate larger, oralternatively, additional batteries and capacitors. The latter of thesetwo options is often more desirable in order to reduce the overall depthof the resulting S-ICD canister 190. Increasing the number of batteriesand capacitors, however, will increase the length and possibly the depthof the S-ICD canister 190. Therefore, numerous S-ICD devices of varyingdepth, widths and lengths are manufactured to accommodate the particularenergy needs of a variety of patient recipients. For example, anoverweight adult male may require a larger and bulkier S-ICD canister190 than a young child. In particular, the young child is generallysmaller, has a relatively lower resistance to current flow, and containsless current diverting body mass than the overweight adult male. As aresult, the energy required to deliver an effective therapy to the youngchild's heart may be considerably less than for the overweight adultmale, and therefore, the young child may utilize a smaller and morecompact S-ICD canister 190. In addition, one may find that individuals,despite equivalent body size, may have different therapy requirementsbecause of differences in their underlying heart disease. This may allowsome patients to receive a smaller canister compared to another patientof equal body size but with a different type of heart disease.

[0082] The spatial requirements of a resulting S-ICD canister 190 areadditionally dependent upon the type of operational circuitry usedwithin the device. The S-ICD canister 190 may be programmed to monitorcardiac rhythms for tachycardia and fibrillation, and if detected, willinitiate charging the capacitor(s) to deliver the appropriatecardioversion/defibrillation energy. Examples of such circuitry aredescribed in U.S. Pat. Nos. 4,693,253 and 5,105,810, and areincorporated herein by reference. The S-ICD canister 190 mayadditionally be provided with operational circuitry for transthoraciccardiac pacing. This optional circuitry monitors the heart forbradycardia and/or tachycardia rhythms. In the event a bradycardia ortachycardia rhythm is detected, the operational circuitry delivers theappropriate pacing energy at the appropriate intervals to treat thedisorder.

[0083] In additional embodiments, the operational circuitry may be: 1)programmed to deliver low amplitude shocks on the T-wave for inductionof ventricular fibrillation for testing the S-ICD canister'sperformance; 2) programmed for rapid ventricular pacing to either inducea tachyarrhythmia or to terminate one; 3) programmed to detect thepresence of atrial fibrillation; and/or 4) programmed to detectventricular fibrillation or ventricular tachycardia by examining QRSwaves, all of which are described in detail above. Additionaloperational circuitry, being known in the art for sensing, shocking andpacing the heart, are additionally incorporated herein as being withinthe spirit and scope of the present invention.

[0084] The primary function of the canister housing 192 is to provide aprotective barrier between the electrical components held within itsconfines and the surrounding environment. The canister housing 192,therefore, must possess sufficient hardness to protect its contents.Materials possessing this hardness may include numerous suitablebiocompatible materials such as medical grade plastics, ceramics, metalsand alloys. Although the materials possessing such hardnesses aregenerally rigid, in particular embodiments, it is desirable to utilizematerials that are pliable or compliant. More specifically, it isdesirable that the canister housing 192 be capable of partially yieldingin its overall form without fracturing.

[0085] Compliant canister housings 192 often provide increased comfortwhen implanted in patient recipients. S-ICD canisters 190 formed fromsuch materials permit limited, but significant, deflection of thecanister housing 192 with certain thoracic motions. Examples ofpermitted deflections are ones that are applied to the canister housing192 by surrounding muscle tissue. The use of a compliant canisterhousing is particularly beneficial in canister housing embodiments thatextend over a significant portion of a patient's thorax. The compliantmaterial in these embodiment may comprise a portion of the canisterhousing, or alternatively, may comprise the canister housing in itsentirety. The correct material selection (or combination thereof),therefore, is helpful in eliminating patient awareness of the device andin improving the long-term wearability of the implanted device.

[0086] Materials selected for the canister housing 192 should further becapable of being sterilized. Often commercial sterilization processesinvolve exposure to elevated temperatures, pressures or chemicaltreatments. It is important, therefore, that the materials used informing the canister housing be capable of withstanding such exposureswithout degrading or otherwise compromising their overall integrity.

[0087] Polymeric materials suitable for the canister housing 192 of thepresent invention include polyurethanes, polyamides,polyetheretherketones (PEEK), polyether block amides (PEBA),polytetrafluoroethylene (PTFE), silicones, and mixtures thereof. Ceramicmaterials suitable for the canister housing 192 of the present inventioninclude zirconium ceramics and aluminum-based ceramics. Metallicmaterials suitable for the canister housing 192 of the present inventioninclude stainless steel, and titanium. Alloys suitable for the canisterhousing 192 of the present invention include stainless steel alloys andtitanium alloys such as nickel titanium. In certain embodiments of thepresent invention, classes of materials may be combined in forming thecanister housing 192. For example, a nonconductive polymeric coating,such as parylene, may be selectively applied over a titanium alloycanister housing 192 surface in order to allow only a specific surfacearea, such as that at the undersurface of the duckbill distal end, toreceive signals and/or apply therapy.

[0088] In general, it is desirable to maintain the size of the S-ICDcanister housing 192 under a total volume of approximately 50 cubiccentimeters. In alternative embodiments of the present invention, it isdesirable to maintain the size of the S-ICD canister housing 192 under atotal volume of approximately 100 cubic centimeters. In yet alternativeembodiments of the present invention, it is desirable to maintain thesize of the S-ICD canister housing 192 under a total volume ofapproximately 120 cubic centimeters.

[0089] Moreover, it is additionally desirable to maintain the totalweight of the S-ICD canister 190, as a whole (including the canisterhousing, operational circuitry, capacitors and batteries), underapproximately 50 grams. In alternative embodiments of the presentinvention, it is desirable to maintain the total weight of the S-ICDcanister 190 under approximately 100 grams. In yet alternativeembodiments of the present invention, it is desirable to maintain thetotal weight of the S-ICD canister 190 under approximately 150 grams.

[0090] Maintaining the weight and size within the above identifiedparameters is primarily for patient comfort depending upon the shape ofthe device. The implantation of a S-ICD canister 190 is a long-termsolution to heart dysfunction, and as such, will ideally remain in thepatient until the device's batteries need replacement or an alternativetherapy eventually leads to its removal. Accordingly, a considerableamount of engineering is devoted to minimizing discomfort associatedwith the installed device.

[0091] Weight and size considerations are particularly important toyounger patient recipients. Children possessing ICDs are more likely tobe cognitive of any additional weight or bulkiness associated withheavier and/or larger devices. The present invention overcomes theseproblems by designing a S-ICD canister 190 that takes into considerationthe concerns of these smaller sized patient recipients. For example,lighter materials may be utilized to minimize discomfort associated withheavier materials. Furthermore, the S-ICD canister 190 (length, widthand depth) in its entirety, or only a portion thereof, may be modifiedin order to accommodate a variety of sized patient recipients. Forexample, the shape of the S-ICD canister housing 192 may also bemanufactured in a variety of anatomical configurations to better insurecomfort and performance in younger children or smaller adults,throughout the life of their S-ICD canisters 190. In order toaccommodate certain patients, a physician may place the canister 190posteriorly with the lead electrode positioned anteriorly with thepatient's body, the reverse of the canister's 190 usual positioning.This canister 190 placement is particularly useful when implanted invery small children. Such canister 190 placement generally optimizescomfort for these smaller stature recipients. Moreover, the shape of thecanister 190 may be altered specifically to conform to a female'sthorax, where breast tissue may alter comfort and performancerequirements.

[0092] Referring now to specific portions of the canister housing 192,FIG. 19 depicts a canister housing 192 in accordance with one embodimentof the present invention having a top surface 194, a bottom surface 196and surrounding sides 198 connecting these two surfaces. The S-ICDcanister housing 192 depicted in FIG. 19 further includes a distal end200 and a proximal end 202. In particular canister housing embodiments,the canister housing 192 may lack a proximal end and a distal end.

[0093] The top surface 194 of the canister housing 192 is generallysmooth and void of appendages and apertures. The smooth top surface 194enables the S-ICD canister 190 to advance effortlessly through thesubcutaneous tissues during an implantation procedure. Smoothing the topsurface 194 reduces the coefficient of friction of the S-ICD canister190. Such measures reduce abrasion, and concurrently, also reduceinflammation associated with the device's insertion and advancement. Thebenefits of a reduction in surface friction also continues on long afterimplantation through a significant reduction in inflammation andsoreness, lending to an overall heightened feeling of wearability andcomfort.

[0094] In alternative embodiments, the top surface 194 of the canisterhousing 192 may include one or more apertures, sensors, electrodes,appendages, or a combination thereof. Apertures on the top surface 194of the canister housing 192 are generally in the form of a connectionport 203, or multiple connection ports, for coupling ancillary devicesto the canister itself. More specifically, the connection ports 203couple the operational circuitry housed within the canister to theseancillary devices, as well as to a lead electrode 191. Connection ports203 may be positioned anywhere along the canister housing 192, however,in particular embodiments, the connection ports 203 are located at thedistal end 200 or proximal end 202 of the canister housing 192. Theconnection ports 203 may additionally be positioned along the canisterhousing's sides 198 and bottom surface 196.

[0095] In yet another embodiment, connection ports 203 are located atboth the distal end 200 and the proximal end 202 of the canister housing192. Positioning connection ports 203 at both the canister's distal end200 and the proximal end 202 may enhance the care provided by the S-ICDcanister 190. In particular, this canister arrangement allows theoperational circuitry in the S-ICD canister 190 to utilize multipleelectrodes and sensors to best regulate and treat the particularcondition experienced by the patient recipient. Examples of ancillarydevices suitable for attachment include a lead 193, such as a lead forsensing, shocking and pacing. Additional ancillary devices suitable forattachment to the S-ICD canister 190, being known in the art, (e.g.,heart failure monitoring sensors) are additionally incorporated as beingwithin the spirit and scope of the present invention.

[0096] The top surface 194 of the canister housing 192 may additionallyinclude particular appendages. Appendages are especially useful inanchoring the canister housing 192 in a fixed relative position, oralternatively, in advancing the canister housing 192 within the patientrecipient. An example of an appendage that may be incorporated into thetop surface 194 of the canister housing 192 is an extending fin. Afin-like appendage may extend from the canister housing 192 in order tobetter direct the S-ICD canister 190 during the implantation procedure.In this capacity, the extended fin acts as a rudder preventing theadvancing S-ICD canister 190 from deviating from its desired path. Theextended fin may additionally aid in preventing the S-ICD canister 190from displacing from its original position afterimplantation—particularly in the direction perpendicular to the fin'slength. Extending fins suitable for the present invention may extend theentire length of the canister housing 192, or alternatively, a segmentof the length. Additionally, extending fins may be disposed on thebottom surface 196 of the canister housing 192 in order to providesimilar functions.

[0097] Appendages may also aid physicians in advancing the S-ICDcanister 190 to a desired location within the patient.Motility-enhancing appendages enable the physician to push, pull orotherwise direct the S-ICD canister 190 in a particular fashionthroughout the patient's body. During the procedure, a physiciangenerally attaches a medical instrument to the motility-enhancingappendage. This attachment step may occur either before or after theS-ICD canister 190 has been inserted within the patient. An example ofone medical instrument capable of attaching to the motility-enhancingappendage is a hemostat. Other similar medical instruments, known tothose skilled in the art, may also be utilized in this attachment step.The physician then advances the hemostat in a desired direction toproperly seat the S-ICD canister 190 within the patient's body.

[0098] The surrounding sides 198 of the canister housing 192 aregenerally smooth and substantially rounded between the top surface 194and the bottom surface 196 of the canister housing 192. Smoothing theside surfaces 198 aids in the insertion of the S-ICD canister 190 duringthe implantation procedure. More specifically, smoother side surfaces198 permit the S-ICD canister 190, as a whole, to slide easily throughthe surrounding bodily tissue while minimizing abrasion. In addition,rounded, smooth transition surfaces allow the surrounding tissues tobetter conform to the presence of the device making the device morecomfortable to the patient during chronic implantation.

[0099] In contrast, sharp edge formations may have the tendency toablate, or at a minimum, irritate the surrounding tissue during theimplantation process. Subsequent tissue irritation may also occur longafter the implantation process. Minor fluctuations in the positioning ofa sharp edged canister may cause an inflammatory response in thesurrounding tissue. These minor fluctuations are often the result ofsimple day-to-day movements. Movement of the arms, bending at the waistand rotation of the torso are all daily activities that may causesurrounding bodily tissue to chafe against the installed canister.Smoothing these edges, however, would greatly reduce tissue abrasion,and thereby, reduce the soreness and discomfort associated with theimplanted S-ICD canister 190.

[0100] Referring now to FIG. 20, the bottom surface 196 of the S-ICDcanister 190 of FIG. 19 is shown. In particular, an electrode 204possessing an electrically conductive surface is depicted within theconfines of, and hermetically sealed within, the S-ICD canister housing192. Although an electrode 204 is specifically illustrated, any sensorcapable of receiving physiological information and/or emitting an energymay be similarly situated on the canister housing 192. For example, asensor may be located on the canister housing 192 that may monitor apatient's blood glucose level, respiration, blood oxygen content, bloodpressure and/or cardiac output.

[0101] Specifically with reference to FIG. 20, the exposed electrode 204is electrically coupled to the operational circuitry encased within thecanister housing 192. The electrode 204, therefore, performs many of thefunctions defined by the operational circuitry's programming. Morespecifically, the electrode 204 is the vehicle that actually receivesthe signals being monitored, and/or emits the energy required to pace,shock or otherwise stimulate the heart. Although only a single electrode204 is shown for illustrative purposes, certain S-ICD canisterembodiments 190 may be manufactured with multiple electrodes. For theseembodiments, the multiple electrodes are often task specific, whereineach electrode 204 performs a single function. In alternate embodiments,a single electrode 204 may perform both monitoring and shockingfunctions.

[0102] The electrodes 204 are generally positioned at the ends 200 and202 of the canister housing 192. In the S-ICD canister 190 depicted inFIG. 20, the electrode 204 is placed at the distal end 200 of thecanister housing 192. Although the electrode 204 is positioned in closeproximity to the distal end 200, the side 198 of the canister housing192 nearest the distal end 200 should generally refrain from exposingany portion of the electrically conductive surface of the electrode 204.Additionally, although the electrode is generally planar, in particularembodiments, the electrode may possess a curved shape.

[0103] The size of the electrically conductive surface of an electrode204, in one particular embodiment, is approximately 500 squaremillimeters in area. In alternate embodiments, it is desirable tomaintain the size of the electrically conductive surface betweenapproximately 100 square millimeters and approximately 2000 squaremillimeters in area. As with the size of the canister housing 192, thesize of the electrically conductive surface may vary to accommodate theparticular patient recipient. Furthermore, the shape and size of anelectrode 204 may vary to accommodate the placement of the electrode 204on the canister housing 192. The shape and size of an electrode may alsobe varied to adapt to specified diagnostic and therapeutic functionsperformed by the canister 190. For example, the electrode's 204 size andshape may be altered to minimize energy loss to surrounding bodilytissues, or for minimizing the diversion of current away from the heart.

[0104] One factor in minimizing current diversion is in maintaining anequal current density distribution throughout an electrode's 204conductive surface. A controlling factor in an electrode's 204 currentdensity distribution is the electrode's 204 overall shape. Certainelectrode 204 shapes draw current to particular areas on the electrode's204 conductive surface (e.g., sharp angles). As a result, theseelectrodes 204 create an unequal current density distribution.Electrodes 204 possessing sharp corners, for example, may have highercurrent densities in the regions defined by the sharp corner. Thisunequal current density distribution results in confined “hot spots”.The formation of hot spots may be desirable and intentional, such aswhen attempting to increase current density adjacent to the sternum. Onthe other hand, hot spots may be undesirable as these high currentdensity locations may scorch or singe surrounding tissue during theelectrode's 204 emission of electrical energy. Moreover, electrodes 204possessing numerous hot spots on the electrode's 204 conductive surfaceto consequently generate areas of low current density—or “cold spots”.This unequal distribution may render the electrode 204, as a whole,highly ineffective.

[0105] Electrode 204 embodiments of the present invention, in contrast,are substantially rounded. In particular, regions of the electrode 204traditionally possessing sharp corners are rounded to prevent extremehot spots. Nevertheless, the distal most segment of the electrode 200 isslightly angulated in order to modestly concentrate current at the tip,and therefore, direct current more through the mediastinum and into thepatient's heart.

[0106] Another controlling factor in an electrode's 204 current densitydistribution is the electrode's 204 overall size. The relatively smallconductive surfaces of electrodes 204 of the present invention, asdiscussed above, minimize the likelihood of forming either hot or coldspots. Larger electrodes, in contrast, possess large surface areas thatmay be more prone to generate more regions of unequal currentdistribution.

[0107] As discussed above, electrodes 204 may vary in shape and size toaccommodate an assortment of canister housing 192 designs. Forillustrative purposes, FIG. 20 and FIGS. 23A-25A show various electrodeshapes disposed upon various canister housings 192. The canisterhousings 192 depicted in these figures, however, are not limited to theelectrode shape specifically illustrated.

[0108] The electrode 204 depicted in FIG. 20 is “thumbnail” shaped. Thedistal end margin 206 of this shaped electrode 204 generally follows theoutline of the rounded distal end 200 of the canister housing 192. Asthe electrode 204 moves proximally along the length of the canisterhousing 192, the conductive surface terminates. In the thumbnailembodiment, the electrode's conductive surface is generally containedwithin the rounded portions of the distal end 200 of the canisterhousing 192. In alternate embodiments, the electrode's conductivesurface may extend proximally further within the canister housing 192.In yet another thumbnail shaped electrode embodiment, the margins of theelectrode's conductive surface refrain from following the exact roundedcontour of the canister housing 192.

[0109] A “spade” shaped electrode 236 is depicted in FIG. 23A. Thedistal end of the spade shaped electrode also generally follows theoutline of the rounded distal end 234 of the canister housing 220. Asthe spade shaped electrode 236 moves proximally along the length of thecanister housing 220, the conductive surface terminates in a roundedproximal end. Similar to the thumbnail embodiment described above, thespade shaped electrode's conductive surface is generally containedwithin the distal end 234 of the canister housing 220. In alternateembodiments, the spade shape electrode's conductive surface may extendproximally further within the canister housing 220. In yet another spadeshaped electrode 234 embodiment, the margins of the spade shapedelectrode's conductive surface refrain from following the exact roundedcontour of the canister housing 220, but substantially form a spadeshaped configuration.

[0110] A circular shaped electrode 238 is illustrated in FIG. 23B.

[0111] A rectangular shaped electrode 246 is shown in FIG. 24A.Rectangular shaped electrodes 246 also incorporate electrodes that aresubstantially rectangular in shape. In particular to FIG. 24A, thecorners of the rectangular shaped electrode 246 are rounded. Moreover,one margin of the rectangular shaped electrode's conductive surfacegenerally follows the rounding of the distal end 246 of the canisterhousing 241.

[0112] A triangular shaped electrode 254 is depicted in FIG. 24B.Triangular shaped electrodes 254 also incorporate electrodes that aresubstantially triangular in shape. In particular to FIG. 24B, thecorners of the triangular shaped electrode 254 are rounded.

[0113] A square shaped electrode 257 is depicted in FIG. 24C. Squareshaped electrodes 257 also incorporate electrodes that are substantiallysquare in shape. In particular to FIG. 24C, the corners of the squareshaped electrode 257 are rounded.

[0114] An ellipsoidal shaped electrode 268 is depicted in FIG. 25A. Thedistal end of the ellipsoidal shaped electrode 268 generally follows theoutline of the rounded distal end 264 of the canister housing 260. Asthe ellipsoidal shaped electrode 268 moves proximally along the lengthof the canister housing 260, the conductive surface elongates and thenagain reduces in length to form a rounded proximal end. Similar to thethumbnail and spade shaped embodiments described above, the ellipsoidalshaped electrode's conductive surface is generally contained within thedistal end 264 of the canister housing 260. In alternate embodiments,the ellipsoidal shape electrode's conductive surface may extendproximally further within the canister housing 260. In yet anotherellipsoidal shaped electrode 264 embodiment, the margins of theellipsoidal shaped electrode's conductive surface refrain from followingthe exact rounded contour of the canister housing 260, but substantiallyform an ellipsoidal shaped configuration.

[0115] Energy emissions from any of the above described electrodes 204generally follow a path of least resistance. The intended pathway of theemission, therefore, may not necessarily be the pathway that theemission ultimately travels. This is particularly a problem withemissions made within the human anatomy where tissue conductivities arehighly variable. Obstructing, or low conductivity tissues like bonematerial, fat, and aerated lung may all redirect released energy awayfrom the heart. Alternatively, surrounding non-cardiac or striatedmuscle tissue, being generally a high conductivity tissue, may divertenergy emissions away from the heart. This is a particular concern forthe pectoralis, intercostal, and latissimus dorsus musculature, as wellas other thoracic, non-cardiac musculature found between the treatingelectrodes of the S-ICD. Since the S-ICD canister 190 of the presentinvention does not directly contact the heart muscle itself, such lowand high conductivity tissues will impede and/or shunt a percentage ofthe emissions from the present invention's electrode 204 permitting theheart to receive a fraction of the total emitted energy.

[0116] The present invention minimizes the effect of impeding and/orobstructing tissues by designing an electrode 204 and canister housing192 capable of focusing the electrode's array of emitted energy.Focusing the electrode's array of energy into a highly concentrated beamenables the resulting beam to be only minimally impeded or shunted awayby any surrounding bodily tissue. This focused array, therefore,delivers more of the originally emitted energy directly into themediastinum, and subsequently, into the intended heart muscle than wouldotherwise occur if the entire canister, or a majority of the canister,were electrically active—as is the case with standard transvenous ICDsystems. The present invention provides an electrode 204 and canisterhousing 192 design that creates a consistently focused array of energydirected toward the chambers of a recipient's heart.

[0117] Generally, it is desirable to have the electrode's longestconductive surface plane positioned perpendicular to the extending ribswithin a recipient's rib cage. Aligning the electrode 204 in this mannerremoves the longest conductive plane from possibly extending directlyover any one particular rib. If the longest conductive surface were toextend along the length of a rib, a greater percentage of emitted energywould be distributed through the rib material, and consequently, mayfail to reach the heart muscle. When aligned perpendicular to the ribs,only a portion of the conductive surface is directly over any particularrib. This alignment permits only a small percentage of the emittedenergy to be obstructed by the impeding rib material. Therefore, inparticular S-ICD canister 190 embodiments that extend parallel with arecipient's rib cage, the width 205 of the electrode's conductivesurface is approximately greater than or equal to the length 207 of theelectrode's conductive surface. This electrode 204 sizing is bestillustrated with reference to FIG. 20. The conductive surface of thethumbnail-shaped electrode in FIG. 20 is depicted as both shallow andwide. In contrast, S-ICD canister 190 embodiments that extendperpendicular with a recipient's rib cage, can have their conductivesurface's length 207 being greater than their conductive surface's width205. The appropriate S-ICD canister 190 alignment, and subsequently theappropriate electrode 204 alignment, is determined by the style of S-ICDcanister 190 chosen for the patient recipient. FIGS. 23A-26C illustratenumerous S-ICD canister housing embodiments 192 for properly positioningan electrode 204 over a recipient's heart. The embodiments depicted,however, are for illustrative purposes only, and are not intended tolimit the scope of the present invention.

[0118] Another solution to the problem of thoracic tissues interferingwith energy delivery is by designing a canister housing 192 that may bestrategically positioned in close proximity to the patient's heart. Oneembodiment of the present invention possesses a curved canister housing192 that enables the S-ICD canister 190 to be advanced just over thepatient recipient's ribcage. Moreover, in another embodiment, thecurvature of the S-ICD canister 190 directly mimics the naturalcurvature of the ribcage.

[0119] Referring now to FIG. 21, the S-ICD canister 190 of FIG. 19 isshown from the side. FIG. 21 shows the S-ICD canister's top surface 194,the bottom surface 196 and the side 198 of the canister housing 192. Inthe embodiment depicted, both the top surface 194 and the bottom surface196 of the canister housing 192 are curved. In fact, throughout most ofthe proximal end 202 of the canister housing 192, the curvature isgenerally similar, and indeed can be identical, between the top surface194 and the bottom surface 196. In alternative embodiments of thepresent invention, the top surface 194 may be generally planar while thebottom surface 196 is curved. In yet another embodiment of the presentinvention, the top surface 194 may be curved and the bottom surface 196is generally planar.

[0120] Referring back to the embodiment depicted in FIG. 21, thecurvatures between the top surface 194 and the bottom surface 196 areshown differing toward the distal end 200 of the rug canister housing192. At the S-ICD canister's distal end 200, the canister housing's topsurface 194 curvature tapers downwardly toward the canister's bottomsurface 196. This tapering causes the distal end 200 of the canisterhousing 192 to be narrower (of a decreased depth) than the canister'sproximal end 202. In certain embodiments, this tapering in depth may begradual throughout the length of the canister's housing 192, oralternatively, the tapering may be confined to a particular area.

[0121] Tapering the depth of the canister housing 192 may improve theoverall performance of the S-ICD canister 190. In particular, a tapereddistal end 200 may aid in insertion and advancement of the S-ICDcanister 190 within the patient recipient's body. A tapered distal end200 enables the S-ICD canister 190 to easily traverse through narrowsubcutaneous spaces. In particular, a physician generally tries tocreate a passageway into the patient's body that is appropriately sizedfor the canister, especially in regard to positioning the distal segmentof the canister with the end containing the electrode in close proximityto the sternum. Tapering the distal end of the canister eliminatesunnecessary trauma to the patient in the tight spaces adjacent to thesternum. For larger canisters, however, this tight subcutaneous space isdifficult to traverse. Subsequently, these larger canisters cause thephysician to undertake extensive sharp and blunt dissection of thepatient's tissues in order to place the larger canister in the desiredlocation. Regardless of the extent of the dissection, however, largernon-tapered distal segments may prove extremely uncomfortable if forcedinto a parasternal position to satisfy the needs of focusing energythrough the mediastinum, and subsequently, to the patient's heart.

[0122] In contrast, embodiments of the present invention having narrowcanister housings 192 may easily traverse such passageways. Moreover,tapering the S-ICD canister's distal end 200 further streamlines thecanister housing 192, and therefore, enhances the ease of theimplantation procedure. Tapering the S-ICD canister's distal end 200 isparticularly important when positioning the distal end of the canisterhousing as near the left border of a patient's sternum as possible. Thiscanister housing 192 placement optimizes energy delivery to themediastinum, and therefore, to the patient's heart.

[0123] The depth of the canister housing 192 is shown as being verynarrow as to the canister housing's length 207. The canister's housingdepth is less than approximately 15 millimeters. In alternateembodiments, the depth of the canister's housing depth is approximately5 millimeters to approximately 10 millimeters. At the tapered distal end200, the canister housing may have a depth of approximately 1-4millimeters

[0124] In certain embodiments of the present invention, it is desirableto position the S-ICD canister 190 in close proximity to the patientrecipient's heart, without directly contacting the heart. A favoredlocation for this S-ICD canister 190 placement is just over thepatient's ribcage. More particularly, in certain embodiments it isfavored to place the S-ICD canister 190 just to the left of, andadjacent to, the sternum with a segment at the distal end 200 containingthe electrode 204 closest to the sternum. FIG. 22 depicts the placementof the S-ICD canister 190 according to one embodiment of the presentinvention with the lead electrode traversing the subcutaneous tissueslaterally toward the axilla and then posteriorly to “catch” the currentas it is emitted from electrode 204 parasternally and anteriorly towardthe lead electrode 191 as it receives current exiting the posteriormediastinum and paraspinal tissues.

[0125] During the implantation procedure, a single incision 210 is madein the left anterior axillary line approximately at the level of thecardiac apex, or around the fifth to the sixth intercostal space. Thelocation of this single incision 210 enables the physician to positionboth the S-ICD canister 190 and the canister's ancillary devices (e.g.,pacing leads, shocking leads, etc.) from this single incision 210. Oncethis incision 210 is made, the physician may insert surgical instrumentsor a specially designed tool (not shown) through the incision 210 toshape a passageway for the S-ICD canister 190 to navigate. Although atool may be utilized in particular embodiments, a tool is notrequired—standard surgical instruments, together with the general shapeof the S-ICD canister 190, are sufficient to facilitate properpositioning of the device in the left anterior thorax as adjacent aspossible to the sternum.

[0126] In particular embodiments, a physician advances both the S-ICDcanister 190 and the lead electrode 191 within the patient to form adepolarization vector with respect to the patient's heart 218. Thedepolarization vector is a vector having an origin, a first end pointand a second end point.

[0127] In one embodiment, the origin of the depolarization vectororiginates approximately within the chambers of the patient's heart 218.Similarly, the first vector end point comprises the S-ICD canisterelectrode's 204 positioning with respect to the patient's heart 218.Finally, the second vector end point comprises the lead electrode's 191positioning with respect to the patient's heart 218. In alternateembodiments, the second vector end point comprises a second canisterelectrode.

[0128] The lead electrode may be positioned at various positions withinthe body because the length of the lead 193 may be varied. For example,S-ICD devices of the present invention may have leads with lengthsbetween 5 centimeters and 55 centimeters. Therefore, the S-ICD canister190 and lead electrode 191 of the present invention may create numerousdepolarization vectors.

[0129] In particular embodiments, a degree of separation of 180 degreesor less exists between the S-ICD canister electrode 204 and the leadelectrode 191. In alternative embodiments, the degree of separationbetween the S-ICD canister electrode 204 and the lead electrode 191 isapproximately 30 degrees to approximately 180 degrees.

[0130] In order to obtain the desired degree of separation for thedepolarization vector, generally one device (either the S-ICD canister190 or the lead electrode 191) must be advanced anteriorily while theother device is advanced posteriority from the initial incision 210.Accordingly, when the S-ICD canister 190 is advanced subcutaneously andanteriorily from the incision 210, the lead electrode 191 must beadvanced subcutaneously and posteriority from the incision 210. Withthis particular embodiment, a physician may advance the S-ICD canister190 medially toward the patient's left inframammary crease to a locationproximate the patient's sternum 212.

[0131] Alternatively, the physician may advance, and subsequentlyposition the S-ICD canister 190 within the anterior portion of thepatient's ribcage 216. This anterior placement may further include thepatient's left parasternal region, an anterior placement within theregion of the patient's third and the patient's twelfth rib 214, orgenerally any subcutaneous ribcage 216 placement anterior to thepatient's heart 218. In order to complement the S-ICD canister's 190placement, and obtain the correct depolarization vector, the leadelectrode 191 must be advanced posteriority toward the paraspinal orparascapular region of the patient's ribcage 216.

[0132] In another embodiment of the present invention, the spatialpositioning of the S-ICD canister 190 and the lead electrode 191,described in detail above, are reversed.

[0133] Referring back to FIG. 21, the curvature of particular S-ICDcanister embodiments 190 may be designed to generally mimic the naturalcurvature of a patient's ribcage 216. These S-ICD canister embodiments190 restrict canister displacement and heighten comfort for the patientimplanted with the S-ICD canister 190. The anatomical shape of a patientrecipient's ribcage 216 varies. The present invention includes numerousS-ICD canister housing 192 curvatures to accommodate these varyingshapes. In particular, the present invention includes S-ICD canisters190 sized and shaped to properly fit children, as well as ones toproperly fit fully developed adults.

[0134] The curvature of the canister housing 192 is generallyarc-shaped. The degree of curvature for any particular embodiment of thepresent invention is measured through a curvature vector theta (θ). Thecurvature vector θ is a vector having an origin 199, a first end pointand a second end point.

[0135] In one embodiment, the origin 199 of the curvature vector θoriginates approximately at the center of the S-ICD canister 190(lengthwise). The first vector end point in this embodiment comprisesthe distal end 200 of the S-ICD canister 190 and the second vector endpoint comprises the proximal end 202 of the S-ICD canister 190. Inparticular embodiments, the curvature vector θ possesses a degree ofseparation between 30 degrees and 180 degrees. For example, a canisterhousing 192 having a degree of separation of 180 degrees is planar.Decreasing the degree of curvature θ causes the canister housing tobecome more arcuate in shape.

[0136] In alternative embodiments, the origin 199 of the curvaturevector θ may originate at a point other than the center of the S-ICDcanister 190. Origins 199 shifted from the center of the S-ICD canister190 produce regions of greater curvature, as well as areas of lessercurvature, in the same S-ICD canister 190. Similarly, a S-ICD canister190 may possess multiple curvature vectors θ having origins 199throughout the length of the S-ICD canister 190. Multiple curvaturevectors θ produce various non-linear or nonsymmetrical curves that, incertain circumstances, remain generally arc-shaped. Canister housingspossessing multiple curvature vectors θ are particularly suitable forS-ICD canister 190 placement near the patient's sides (generally in thearea under the patient's arms where the thorax has a more marked degreeof curvature). Canister housings 192 incorporating a nonsymmetricalcurvature are generally longer S-ICD canisters 190 that span over thefront and sides of the patient's ribcage. In particular, these S-ICDcanisters 190 span areas of the ribcage 216 that are generally planar(around the patient's sternum 212), as well as areas that are highlycurved (generally in the area under the patient's arms).

[0137] Curved canister housings 192 are generally for S-ICD canisters190 that extend lengthwise, or approximately horizontally, along thelength of the ribs in the ribcage 216. For certain embodiments, however,it is desired to orient the length of the S-ICD canister 190 to beperpendicular to the length of the ribs in the ribcage 216. Aperpendicularly orientated S-ICD canister 190 generally requires verylittle, if any, curvature to conform to the ribcage 216.

[0138] FIGS. 23A-26C depict particular S-ICD canister 190 designs. Ineach of these particular S-ICD canister designs, the various materialconstructions, dimensions and curvatures, discussed in detail above, maybe incorporated within each individual S-ICD canister design.Furthermore, particular aspects of any individual S-ICD canister designmay be incorporated, in whole or in part, into another depicted S-ICDcanister design.

[0139] Turning now to FIG. 23A, a S-ICD canister 220 having aduckbill-shaped canister housing 222 is shown. The duckbill-shapedcanister housing 222 has a proximal end 226 and a distal end 234. Theproximal end 226 of the duckbill-shaped canister housing 222 furtherincludes a main housing member 228 and a distal housing member 230. Thedistal housing member 230 is an elongated segment extending distallyfrom the distal end of the main housing member 228. Although the twosegments differ in their size and shape, the distal housing member 230and main housing member 228 are generally contiguously and fluidlyattached to one another and may be formed from a single mold. Inalternative embodiments, however, the distal housing member 230 may behinged to the main housing member 228. The distal housing member 230also generally comprises a material that is similar in composition tothat forming the main housing member 228. In alternate embodiments,however, the distal housing member 230 may include a material thatpossess enhanced electrically insulated characteristics.

[0140] The main housing member 228 generally encases the operationalcircuitry, batteries and capacitors of the duckbill-shaped S-ICDcanister 220. The width and length of the main housing member 228 enablethe main housing member 228 to accommodate batteries and capacitors fordelivering a shocking energy of approximately 50 J of energy, 75 J ofenergy, 100 J of energy, 125 J of energy, 150 J of energy and 200 J ofenergy.

[0141] Although a specific number of batteries and capacitors arerequired for delivering these charges, their positioning within thecanister housing 222 is highly modifiable. More specifically, the widthof the main housing member 228 may be altered to accommodate a longer orshorter canister. For example, the width of the main housing member 228may be increased in order to obtain a main canister housing 228 ofdecreased length. Modification of the sizing and orientation of the mainhousing member 228 allow manufacturers to create a variety of differingsized duckbill-shaped S-ICD canisters 220. Increased specificity in thecanister housing's shape and size enhance the comfort and wearabilityfor the patient recipient.

[0142] In general, the width of the main housing member 228 isapproximately 10 cm wide or less. Likewise, the length of the mainhousing member 228 is approximately 20 cm long or less. In particularembodiments the width of the main housing member 228 is 4 cm. In analternative embodiment, the width of the main housing member 228 is 8cm.

[0143] The distal housing member 230 is an elongated segment of canisterhousing that possesses a width that differs from that of the mainhousing member 228. The distal housing member's width decreases as thedistal housing member 230 extends distally. This tapering in widthresults in the formation of a shoulder region 232. In particularembodiments, the rate with which the width decreases as the proximalhousing member 230 extends distally is constant. In alternateembodiments, the rate is variable. A variable rate shoulder region 232taper proceeds at a rate of tapering where a unit of tapering width isnot directly related to a unit of length in the distal direction. Ineither of the embodiments, however, bilateral symmetry is maintainedthroughout the length of the distal housing member 230.

[0144] The shoulder region 232 is a generally rounded and smooth regionof the canister housing 222. As discussed in detail above, rounding theedges along the canister's surface enhances insertion of the S-ICDcanister 220. The rounded edges also reduce abrasion and inflammationassociated with short-term and long-term wearability.

[0145] Extending distally beyond the shoulder region 232 is the distalhead 234 of the distal housing member 230. The distal head 234 is thedistal termination point of the duckbill-shaped S-ICD canister 220. Thedistal head 234 includes a generally rounded end. In one embodiment,illustrated in FIG. 23B, the distal head 234 has a width greater thanthe width at a location within the shoulder region 232 of the distalhousing member 230. In alternative embodiments, the distal head's widthis equal to or less than the width at any point in the shoulder region232 of the distal housing member 230, as illustrated in 23A.

[0146] The length of the duckbill-shaped S-ICD canister 220 may dependhighly upon the shape and size of the distal housing member 230. Inparticular embodiments, the duckbill-shaped S-ICD canister 220 isapproximately 30 centimeters long or less. In alternative embodiments,the duckbill-shaped S-ICD canister 220 is approximately 10 centimeter orless. In particular embodiments, the length of the duckbill-shaped S-ICDcanister 220 may be curved, or alternatively, or a portion of the length(i.e., the shoulder region 232 and distal head 234) are curved.

[0147] The electrode 236 for the duckbill-shaped S-ICD canister 220 isgenerally seated within a portion of the distal housing member 230. FIG.23A diagrams in phantom the approximate location of an electrode 236 onthe duckbill-shaped canister housing 222. Although the electrode 236 isdepicted as generally circular in shape (in FIG. 23B), the electrode mayalso be “spade shaped” (depicted in FIG. 23A), thumbnail shaped, square,rectangular, triangular or ellipsoidal. The electrode 236 iselectrically coupled to the operational circuitry within the mainhousing member 228 of the S-ICD canister 220.

[0148] In certain embodiments of the present invention, an associatedfeature of the electrode 236 at the distal end is the presence of amargin of insulated material 237 around the active electrode 236. Themargin of insulated material 237 may aid in directing emitted energyfrom the electrode 236 inwardly toward the patient's heart instead ofdispersing energy outward toward the patient's chest wall. This marginof insulated material 237 typically ranges from 1-5 mm in width and mayextend to the margin of the housing. Moreover, in certain embodiments,the margin of insulated material 237 comprises a ceramic material orother material designed to facilitate focusing of current inward towardthe heart.

[0149] In certain embodiments of the present invention, the electroniccomponents (e.g., circuitry, batteries and capacitors) of the S-ICDcanister 220, are generally absent from the distal housing member 230.As such, the depth of the distal housing member 230 may be greatlyreduced. In these embodiments, a depth of approximately 1 millimeter maybe obtained at the distal head 234 of the duckbill-shaped S-ICD canister220.

[0150] The duckbill-shaped distal housing member 230 enhances navigationduring canister implantation. The distal head 234 of the distal housingmember 230 is blunt at its end to reduce trauma suffered to surroundingtissue during the S-ICD canister's advancement or during chronicimplantation. Similarly, the narrower distal head 234 (width-wise anddepth-wise) is easier to control during the advancement procedure. Thesmaller distal head 234 also enables a physician to navigate the smallerand more compact tissues adjacent to the sternum, which a larger headmight otherwise find unobtainable. Moreover, the narrower distal head234 may be advanced to a location in close proximity to the patientrecipient's heart 218 without concern of distorting or stressing theskin in the left parasternal region.

[0151] The closer the electrode 236 is to the patient's heart 218, theless energy is required to achieve an adequate electric field or currentdensity to defibrillate the heart. A desirable anatomical position forreducing this energy requirement is just lateral to the sternum 212 ofthe patient. The area surrounding the patient's sternum 212 generallylacks a considerable accumulation of bodily tissue. Thus, subcutaneousS-ICD canister 190 positioning over the sternum 212, or some otherlocation just over the rib cage 216, provides a significant lessening ofthe required energy—due to proximity to the heart 218 and a reduction inimpeding surrounding tissue. Positioning an ICD canister of normalcontour in this area has proven difficult, however, and is additionallyaesthetically displeasing. The reduced profile of the duckbill-shapedS-ICD canister 220, however, provides such optimal electrode 236placement in a more aesthetically and less physically obtrusive manner.

[0152] Structurally, a reduction in the energy requirement frees spacewithin the canister housing 222. This space was previously occupied bybatteries and capacitors needed for the higher energy requirements. Thisspace, however, is no longer required. The duckbill-shaped S-ICDcanister 220, therefore, can be smaller in length, width and depth.Eliminating batteries and capacitors also reduces the weight of thepresent invention. As described in detail above, reducing the weight ofthe S-ICD canister enhances patient recipient comfort.

[0153]FIG. 24A illustrates another embodiment of a S-ICD canister havinga generally rectangular-shaped canister housing 240. Therectangular-shaped canister housing 240 includes a top surface 241, abottom surface (not shown) and surrounding sides 248 connecting thesetwo surfaces. The rectangular-shaped canister housing 240 furtherincludes a distal end 242 and a proximal end 244. The electrode 246,shown in phantom, is generally positioned at either the distal end 242or the proximal end 244 of the canister housing 240. In alternativeembodiments, the rectangular-shaped canister housing 240 may include twoor more electrodes 246. When two electrodes are utilized, one electrodeis positioned at the distal end 242 of the canister housing 240 whilethe second electrode is positioned at the proximal end 244 of thecanister housing 240.

[0154] The length of the rectangular-shaped canister housing 240 isapproximately 30 centimeters long. In alternative embodiments, therectangular-shaped canister housing 240 is approximately 10 centimeterlong or less. The width of the rectangular-shaped canister housing 240is approximately 3 centimeters to approximately 10 centimeter wide.

[0155]FIGS. 24B and 24C depict additional embodiments of a S-ICDcanister having a generally square-shaped canister housing 250. Thesquare-shaped canister housing 250 includes a top surface 251, a bottomsurface (not shown) and surrounding sides 252 connecting these twosurfaces. The sides 252 of the square-shaped canister housing aregenerally of the same length. The electrode 254, shown in phantom, isgenerally positioned in the center and to one side of the square-shapedcanister housing 250. A triangular shaped electrode 254 is specificallyillustrated at the corner of the square-shaped canister housing 250 inFIG. 24B. In alternate embodiments, however, the electrode 254 may bepositioned toward the center of one of the sides 252 of thesquare-shaped canister housing 250, or at the center of thesquare-shaped canister housing 250, or rotated more. A square shapedelectrode 257 is specifically illustrated at the side of the canisterhousing 250 in FIG. 24C.

[0156] The length and width of the square-shaped canister housing 250 isapproximately 6 centimeters to approximately 8 centimeter long and wide.

[0157]FIG. 25A depicts yet another embodiment of a S-ICD canister havinga “tongue depressor-shaped” canister housing 260. The tonguedepressor-shaped canister housing 260 includes a top surface 261, abottom surface (not shown) and surrounding sides 262 connecting thesetwo surfaces. The tongue depressor-shaped canister housing 260 furtherincludes a distal end 264 and a proximal end 266. The distal end 264 andthe proximal end 266 of the tongue depressor-shaped canister housing260, however, are rounded. In one embodiment, the rounded ends extendoutwardly away from the canister housing 260 in either the correspondingdistal or proximal direction. The rounded ends generally are circulararc-shaped curves, however, the rounded ends may also be elliptical ornonsymmetrical arc-shaped curves.

[0158] The electrode 268, shown in phantom, is generally positioned ateither the distal end 264 or the proximal end 266 of the canisterhousing 260. In alternative embodiments, the tongue depressor-shapedcanister housing 260 may include two or more electrodes 268. When twoelectrodes are utilized, one electrode is positioned at the distal end264 of the canister housing 260 while the second electrode is positionedat the proximal end 266 of the canister housing 260.

[0159] The length of the tongue depressor-shaped canister housing 260 isapproximately 30 centimeters long or less. In alternative embodiments,the tongue depressor-shaped canister housing 260 is approximately 15centimeter long or less. The width of the tongue depressor-shapedcanister housing 260 is approximately 3 centimeters to approximately 10centimeters wide.

[0160] Referring now to FIG. 25B, where a modified tonguedepressor-shaped canister housing 270 is shown. The modified tonguedepressor-shaped canister housing 270 is similar to the tonguedepressor-shaped S-ICD canister 260 depicted in FIG. 25A, however, themodified tongue depressor-shaped canister housing 270 comprises only hasa single rounded distal end 272. The proximal end 274 of the modifiedtongue depressor-shaped canister housing 270 is generally square.

[0161] FIGS. 26A-26C illustrate another embodiment of a S-ICD canisterhaving a multi-segment canister housing 280. The multi-segment canisterhousing 280 includes at least two canister housing segments that arecoupled together. The S-ICD canister depicted in FIG. 26A, 26B and 26Cspecifically have a distal segment 282 and a proximal segment 284hinged, or otherwise coupled, together.

[0162] The distal segment 282 includes a top surface 292, a bottomsurface (not shown) and surrounding sides 286 connecting these twosurfaces. The distal most end 288 of the distal segment 282 comprises arounded region. An electrode 290 is disposed within this rounded regionof the distal segment 282 (shown in phantom). The electrode 290generally follows the outline of the rounded region of the distal mostend 288 of the canister housing, however, the electrode 290 may compriseof other shapes and sizes.

[0163] In an embodiment of the multi-segment canister housing 280, boththe electrode 290 and the electronics are disposed within the distalsegment 282. In alternative embodiments, the electrode 290 is disposedwithin the distal segment 282 and the electronics are located within theproximal segment 284 of the multi-segment canister housing 280.

[0164]FIG. 26B shows the distal segment 282 of the multi-segmentcanister housing 280 being curved to mimic the anatomical shape of apatient recipient's ribcage 216. In the embodiment depicted, both thetop surface 292 and the bottom surface 294 of the proximal segment 282are curved. The curvature, however, differs at the distal most end 288of the distal segment 282. At the distal segment's distal most end 288,the distal segment's top surface 292 tapers downwardly toward the distalsegment's bottom surface 294. This tapering causes the distal most end288 of the distal segment 282 to be narrower than the distal segment'sdistal end 296. In certain embodiments, this tapering in depth may begradual throughout the length of the distal segment 282, oralternatively, the tapering may be confined to a particular area.

[0165] The proximal segment 284 also includes a top surface 298, abottom surface 300 and surrounding sides 302 connecting these twosurfaces. The proximal segment 284 depicted in FIG. 26B, however, isgenerally planar. In alternative embodiments, depicted in FIG. 26C, theproximal segment 284 may also be curved and may also be of a differentcurvature to that of the distal segment.

[0166] The length of the multi-segment canister housing 280 isapproximately 30 centimeters long or less. In alternative embodiments,the multi-segment canister housing 280 is approximately 20 centimetersor less. In yet another embodiment, the multi-segment canister housing280 is approximately 12 centimeters or less. The width of multi-segmentcanister housing 280 is approximately 3 centimeters to approximately 10centimeters wide.

[0167] Numerous characteristics and advantages of the invention coveredby this document have been set forth in the foregoing description. Itwill be understood, however, that this disclosure is, in many aspects,only illustrative. Changes may be made in details, particularly inmatters of shape, size and arrangement of parts without exceeding thescope of the invention. The invention's scope is defined, of course, inthe language in which the appended claims are expressed.

What is claimed is:
 1. An implantable cardioverter-defibrillator forsubcutaneous positioning between the third rib and the twelfth ribwithin a patient, the implantable cardioverter-defibrillator comprising:a housing, wherein the housing comprises a proximal end having a widthand a distal end having a width and wherein the width of the distal endis less than the width of the proximal end; an electrical circuitlocated within the housing; and an electrode electrically coupled to theelectrical circuit and located on the housing.
 2. The implantablecardioverter-defibrillator of claim 1, wherein at least a portion of thedistal end of the housing is rounded.
 3. The implantablecardioverter-defibrillator of claim 1, wherein at least a portion of theproximal end of the housing is substantially square.
 4. The implantablecardioverter-defibrillator of claim 1, wherein at least a portion of theproximal end of the housing is rounded.
 5. The implantablecardioverter-defibrillator of claim 1, wherein the width of the proximalend of the housing is approximately 1 centimeter to approximately 10centimeters wide.
 6. The implantable cardioverter-defibrillator of claim1, wherein the width of the proximal end of the housing is approximately2 centimeters to approximately 5 centimeters wide.
 7. The implantablecardioverter-defibrillator of claim 1, wherein the width of the distalend of the housing is approximately 1 centimeter to approximately 10centimeters wide.
 8. The implantable cardioverter-defibrillator of claim1, wherein the width of the distal end of the housing is approximately 2centimeters to approximately 5 centimeters wide.
 9. The implantablecardioverter-defibrillator of claim 1, wherein the proximal end of thehousing further comprises a depth, wherein the depth of the proximal endof the housing is less than approximately 15 millimeters.
 10. Theimplantable cardioverter-defibrillator of claim 1, wherein the distalend of the housing further comprises a depth, wherein the depth of thedistal end of the housing is approximately 1 millimeter to approximately15 millimeters.
 11. The implantable cardioverter-defibrillator of claim1, wherein the distal end of the housing further comprises a depth,wherein the depth of the distal end of the housing is approximately 1millimeters to approximately 3 millimeters.
 12. The implantablecardioverter-defibrillator of claim 1, wherein the housing furthercomprises a length, wherein the length of the housing is approximately 3centimeters to approximnately 30 centimeters long.
 13. The implantablecardioverter-defibrillator of claim 1, wherein the housing furthercomprises a length, wherein the length of the housing is approximately 5centimeters to approximately 20 centimeters long.
 14. The implantablecardioverter-defibrillator of claim 1, wherein the housing issubstantially bilaterally symmetrical along the housing's length. 15.The implantable cardioverter-defibrillator of claim 1, wherein theproximal end of the housing is hinged to the distal end of the housing.16. The implantable cardioverter-defibrillator of claim 1, wherein theproximal end of the housing is contiguous with the distal end of thehousing.
 17. The implantable cardioverter-defibrillator of claim 1,wherein at least a portion of the housing comprises an electricallyinsulated material.
 18. The implantable cardioverter-defibrillator ofclaim 1, wherein at least a portion of the housing comprises anelectrically nonconductive material.
 19. The implantablecardioverter-defibrillator of claim 1, wherein the housing comprises aceramic material.
 20. The implantable cardioverter-defibrillator ofclaim 1, wherein the housing comprises a titanium alloy.
 21. Theimplantable cardioverter-defibrillator of claim 1, wherein the housingcomprises a polymeric material.
 22. The implantablecardioverter-defibrillator of claim 21, wherein the polymeric materialis selected from the group consisting essentially of a polyurethane, apolyamide, a polyetheretherketone (PEEK), a polyether block amide(PEBA), a polytetrafluoroethylene (PTFE), a silicone, and mixturesthereof.
 23. The implanatble cardioverter-defibrillator of claim 1,wherein at least a portion of the housing is substantially non planar.24. The implantable cardioverter-defibrillator of claim 1, wherein atleast a portion of the housing is substantially planar.
 25. Theimplantable cardioverter-defibrillator of claim 1, wherein theelectrical circuit can provide cardioversion-defibrillation for thepatient's heart.
 26. The implantable cardioverter-defibrillator of claim25 wherein the electrical circuit can further provide multiphasicwaveform cardiac pacing for the patient's heart.
 27. The implantablecardioverter-defibrillator of claim 1, wherein the electrical circuitcan provide multiphasic waveform cardiac pacing for the patient's heart.28. The implantable cardioverter-defibrillator of claim 27, wherein theelectrical circuit can provide biphasic waveform cardiac pacing for thepatient's heart.
 29. The implantable cardioverter-defibrillator of claim27, wherein the electrical circuit can provide triphasic waveformcardiac pacing for the patient's heart.
 30. The implantablecardioverter-defibrillator of claim 27, wherein the electrical circuitcan further provide monophasic waveform cardiac pacing for the patient'sheart.
 31. The implantable cardioverter-defibrillator of claim 1,wherein the electrode can emit an energy for shocking the patient'sheart.
 32. The implantable cardioverter-defibrillator of claim 31,wherein the energy for shocking the patient's heart is approximately 50joules to approximately 75 joules.
 33. The implantablecardioverter-defibrillator of claim 31, wherein the energy for shockingthe patient's heart is approximately 75 joules to approximately 100joules.
 34. The implantable cardioverter-defibrillator of claim 31,wherein the energy for shocking the patient's heart is approximately 100joules to approximately 125 joules.
 35. The implantablecardioverter-defibrillator of claim 31, wherein the energy for shockingthe patient's heart is approximately 125 joules to approximately 150joules.
 36. The implantable cardioverter-defibrillator of claim 35,wherein the energy for shocking the patient's heart is approximately 150J.
 37. The implantable cardioverter-defibrillator of claim 31, whereinthe electrode can receive sensory information.
 38. The implantablecardioverter-defibrillator of claim 1, wherein the electrode can receivesensory information.
 39. The implantable cardioverter-defibrillator ofclaim 1, wherein at least a portion of the electrode is non-planar. 40.The implantable cardioverter-defibrillator of claim 1, wherein theelectrode is substantially circular in shape.
 41. The implantablecardioverter-defibrillator of claim 1, wherein the electrode issubstantially ellipsoidal in shape.
 42. The implantablecardioverter-defibrillator of claim 1, wherein the electrode issubstantially square in shape.
 43. The implantablecardioverter-defibrillator of claim 1, wherein the electrode issubstantially rectangular in shape.
 44. The implantablecardioverter-defibrillator of claim 1, wherein the electrode issubstantially triangular in shape.
 45. The implantablecardioverter-defibrillator of claim 1, wherein the electrode issubstantially thumbnail shaped.
 46. The implantablecardioverter-defibrillator of claim 1, wherein the electrode issubstantially spade shaped.
 47. The implantablecardioverter-defibrillator of claim 1, wherein the housing furthercomprises a connection port electrically coupled to the electricalcircuit.
 48. The implantable cardioverter-defibrillator of claim 47,wherein the connection port is coupled to a lead.
 49. The implantablecardioverter-defibrillator of claim 48, wherein the lead is a pacinglead.
 50. The implantable cardioverter-defibrillator of claim 48,wherein the lead is a shocking lead.
 51. The implantablecardioverter-defibrillator of claim 48, wherein the lead is a sensorylead.
 52. A duckbill-shaped implantable cardioverter-defibrillatorcomprising: a main housing member having a length, a width and a depth;a distal housing member extending proximally from the main housingmember, wherein the distal housing member has a length, a width and adepth; an electrical circuit located within the main housing member; andan electrode electrically coupled to the electrical circuit and locatedon the distal housing member.
 53. The duckbill-shaped implantablecardioverter-defibrillator of claim 52, wherein the length of theduckbill-shaped implantable cardioverter-defibrillator is approximately5 centimeters to approximately 20 centimeters long.
 54. Theduckbill-shaped implantable cardioverter-defibrillator of claim 52,wherein the length of the duckbill-shaped implantablecardioverter-defibrillator is less than 30 centimeters long.
 55. Theduckbill-shaped implantable cardioverter-defibrillator of claim 52,wherein the duckbill-shaped implantable cardioverter-defibrillator issubstantially bilaterally symmetrical along thecardioverter-defibrillator's length.
 56. The duckbill-shaped implantablecardioverter-defibrillator of claim 52, wherein the proximal housingmember is in fluid communication with the main housing member.
 57. Theduckbill-shaped implantable cardioverter-defibrillator of claim 52,wherein the proximal housing member is contiguous with the main housingmember.
 58. The duckbill-shaped implantable cardioverter-defibrillatorof claim 52, wherein the distal housing member is hinged to the mainhousing member.
 59. The duckbill-shaped implantablecardioverter-defibrillator of claim 52, wherein the distal housingmember further includes a distal end, wherein at least a portion of thedistal end of the distal housing member is curved.
 60. Theduckbill-shaped implantable cardioverter-defibrillator of claim 52,wherein the main housing member further includes a proximal end, whereinat least a portion of the proximal end of the main housing member issubstantially square.
 61. The duckbill-shaped implantablecardioverter-defibrillator of claim 52, wherein the main housing memberfurther includes a proximal end, wherein at least a portion of theproximal end of the main housing member is rounded.
 62. Theduckbill-shaped implantable cardioverter-defibrillator of claim 52,wherein the width of the main housing member is approximately 3centimeters to approximately 30 centimeters wide.
 63. Theduckbill-shaped implantable cardioverter-defibrillator of claim 52,wherein the main housing member is approximately 3 centimeters toapproximately 20 centimeters wide.
 64. The duckbill-shaped implantablecardioverter-defibrillator of claim 52, wherein the distal housingmember further comprises a shoulder region, wherein the shoulder regionextends distally from the main housing member.
 65. The duckbill-shapedimplantable cardioverter-defibrillator of claim 64, wherein the shoulderregion of the distal housing member has a width that is less than thewidth of the main housing member.
 66. The duckbill-shaped implantablecardioverter-defibrillator of claim 65, wherein at least a portion ofthe width of the shoulder region decreases as the shoulder regionextends distally from the main housing member.
 67. The duckbill-shapedimplantable cardioverter-defibrillator of claim 66, wherein the width ofthe shoulder region decreases proportionally as the shoulder regionextends distally from the main housing member.
 68. The duckbill-shapedimplantable cardioverter-defibrillator of claim 64, wherein the distalhousing member further comprises a distal head, wherein the distal headextends distally from the shoulder region and defines a distal end ofthe distal housing member.
 69. The duckbill-shaped implantablecardioverter-defibrillator of claim 68, wherein the distal head of thedistal housing member has a width that is less than the width of theshoulder region of the distal housing member.
 70. The duckbill-shapedimplantable cardioverter-defibrillator of claim 68, wherein the distalhead of the distal housing member has a width that is greater than thewidth of the shoulder region of the distal housing member.
 71. Theduckbill-shaped implantable cardioverter-defibrillator of claim 52,wherein the depth of the distal housing member is less than the depth ofthe main housing member.
 72. The duckbill-shaped implantablecardioverter-defibrillator of claim 52, wherein the depth of the distalhousing member is less than approximately 15 millimeters.
 73. Theduckbill-shaped implantable cardioverter-defibrillator of claim 52,wherein the depth of the main housing member is approximately 1millimeter to approximately 15 millimeters.
 74. The duckbill-shapedimplantable cardioverter-defibrillator of claim 52, wherein the depth ofthe main housing member is approximately 1 millimeter to approximately10 millimeters.
 75. The duckbill-shaped implantablecardioverter-defibrillator of claim 52, wherein at least a portion ofthe distal housing member is substantially non-planar.
 76. Theduckbill-shaped implantable cardioverter-defibrillator of claim 52,wherein at least a portion of the main housing member is substantiallyplanar.
 77. The duckbill-shaped implantable cardioverter-defibrillatorof claim 52, wherein at least a portion of the main housing member issubstantially non-planar.
 78. The duckbill-shaped implantablecardioverter-defibrillator of claim 52, wherein the distal housingmember is bilaterally symmetrical along its length.
 79. Theduckbill-shaped implantable cardioverter-defibrillator of claim 52,wherein at least a portion of the distal housing member comprises anelectrically insulated material.
 80. The duckbill-shaped implantablecardioverter-defibrillator of claim 52, wherein at least a portion ofthe distal housing member comprises an electrically non-conductivematerial.
 81. The duckbill-shaped implantable cardioverter-defibrillatorof claim 52, wherein the main housing member comprises a ceramicmaterial.
 82. The duckbill-shaped implantable cardioverter-defibrillatorof claim 52, wherein the main housing member comprises a titanium alloy.83. The duckbill-shaped implantable cardioverter-defibrillator of claim52, wherein the main housing member comprises a stainless steel alloy.84. The duckbill-shaped implantable cardioverter-defibrillator of claim52, wherein the main housing member comprises a polymeric material. 85.The duckbill-shaped implantable cardioverter-defibrillator of claim 84,wherein the polymeric material is selected from the group consistingessentially of a polyurethane, a polyamide, a polyetheretherketone(PEEK), a polyether block amide (PEBA), a polytetrafluoroethylene(PTFE), a silicone, and mixtures thereof.
 86. The duckbill-shapedimplantable cardioverter-defibrillator of claim 52, wherein theelectrical circuit can provide cardioversion-defibrillation for thepatient's heart.
 87. The duckbill-shaped implantablecardioverter-defibrillator of claim 86, wherein the electrical circuitcan provide multiphasic waveform cardiac pacing for the patient's heart.88. The duckbill-shaped implantable cardioverter-defibrillator of claim52, wherein the electrical circuit can provide multiphasic waveformcardiac pacing for the patient's heart.
 89. The duckbill-shapedimplantable cardioverter-defibrillator of claim 88, wherein theelectrical circuit can provide biphasic waveform cardiac pacing for thepatient's heart.
 90. The duckbill-shaped implantablecardioverter-defibrillator of claim 88, wherein the electrical circuitcan provide triphasic waveform cardiac pacing for the patient's heart.91. The duckbill-shaped implantable cardioverter-defibrillator of claim52, wherein the electric circuit can provide monophasic waveform cardiacpacing for the patient's heart.
 92. The duckbill-shaped implantablecardioverter-defibrillator of claim 52, wherein the electrode can emitan energy for shocking the patient's heart.
 93. The duckbill-shapedimplantable cardioverter-defibrillator of claim 92, wherein the energyfor shocking the patient's heart is approximately 50 joules toapproximately 75 joules.
 94. The duckbill-shaped implantablecardioverter-defibrillator of claim 92, wherein the energy for shockingthe patient's heart is approximately 75 joules to approximately 100joules.
 95. The duckbill implantable cardioverter-defibrillator of claim92, wherein the energy for shocking the patient's heart is approximately100 joules to approximately 125 joules.
 96. The duckbill-shapedimplantable cardioverter-defibrillator of claim 92, wherein the energyfor shocking the patient's heart is approximately 125 joules toapproximately 150 joules.
 97. The duckbill-shaped implantablecardioverter-defibrillator of claim 96, wherein the energy for shockingthe patient's heart is approximately 150 J.
 98. The duckbill-shapedimplantable cardioverter-defibrillator of claim 92, wherein theelectrode can receive sensory information.
 99. The duckbill-shapedimplantable cardioverter-defibrillator of claim 52, wherein theelectrode can receive sensory information.
 100. The duckbill-shapedimplantable cardioverter-defibrillator of claim 52, wherein at least aportion of the electrode is non-planar.
 101. The duckbill-shapedimplantable cardioverter-defibrillator of claim 52, wherein theelectrode is substantially circular in shape.
 102. The duckbill-shapedimplantable cardioverter-defibrillator of claim 52, wherein theelectrode is substantially ellipsoidal in shape.
 103. Theduckbill-shaped implantable cardioverter-defibrillator of claim 52,wherein the electrode is substantially square in shape.
 104. Theduckbill-shaped implantable cardioverter-defibrillator of claim 52,wherein the electrode is substantially rectangular in shape.
 105. Theduckbill-shaped implantable cardioverter-defibrillator of claim 52,wherein the electrode is substantially triangular in shape.
 106. Theduckbill-shaped implantable cardioverter-defibrillator of claim 52,wherein the electrode is substantially thumbnail shaped.
 107. Theduckbill-shaped implantable cardioverter-defibrillator of claim 52,wherein the electrode is substantially spade shaped.
 108. Theduckbill-shaped implantable cardioverter-defibrillator of claim 52,wherein the main housing member further comprises a connection port thatelectrically couples to the electrical circuit.
 109. The duckbill-shapedimplantable cardioverter-defibrillator of claim 108, wherein theconnection port is coupled to a lead.
 110. The duckbill-shapedimplantable cardioverter-defibrillator of claim 109, wherein the lead isa pacing lead.
 111. The duckbill-shaped implantablecardioverter-defibrillator of claim 109, wherein the lead is a shockinglead.
 112. The duckbill-shaped implantable cardioverter-defibrillator ofclaim 109, wherein the lead is a sensory lead.
 113. A method ofinserting an implantable cardioverter-defibrillator within a patient,the method comprising the steps of: providing a duckbill-shapedcardioverter-defibrillator comprising a housing, an electrical circuitlocated within the housing, and an electrode located on the housing,wherein the duckbill-shaped cardioverter-defibrillator is configured tomaintain the electrode in a predetermined relationship subcutaneouslyover a patient's ribcage; making a single incision on a patient'sthorax; and advancing the duckbill-shaped cardioverter-defibrillatorthrough the single incision and subcutaneously over a patient's ribcage.114. The method of claim 113, wherein the housing comprises a proximalend having a width and a distal end having a width and wherein the widthof the distal end is less than the width of the proximal end.
 115. Themethod of claim 114, wherein at least a portion of the distal end of thehousing is rounded.
 116. The method of claim 114, wherein at least aportion of the proximal end of the housing is substantially square. 117.The method of claim 114, wherein at least a portion of the proximal endof the housing is rounded.
 118. The method of claim 114, wherein thewidth of the proximal end of the housing is approximately 1 centimeterto approximately 10 centimeters wide.
 119. The method of claim 114,wherein the width of the proximal end of the housing is approximately 2centimeters to approximately 5 centimeters wide.
 120. The method ofclaim 114, wherein the width of the distal end of the housing isapproximately 1 centimeter to approximately 10 centimeters wide. 121.The method of claim 114, wherein the width of the distal end of thehousing is approximately 2 centimeters to approximately 5 centimeterswide.
 122. The method of claim 114, wherein the proximal end of thehousing further comprises a depth, wherein the depth of the proximal endof the housing is less than approximately 15 millimeters.
 123. Themethod of claim 114, wherein the distal end of the housing furthercomprises a depth, wherein the depth of the distal end of the housing isapproximately 1 millimeter to approximately 15 millimeters.
 124. Themethod of claim 114, wherein the distal end of the housing furthercomprises a depth, wherein the depth of the distal end of the housing isapproximately 1 millimeter to approximately 3 millimeters.
 125. Themethod of claim 113, wherein the housing further comprises a length,wherein the length of the housing is approximately 3 centimeters toapproximately 30 centimeters long.
 126. The method of claim 113, whereinthe housing further comprises a length, wherein the length of thehousing is approximately 5 centimeters to approximately 20 centimeterslong.
 127. The method of claim 113, wherein the housing is substantiallybilaterally symmetrical along the housing's length.
 128. The method ofclaim 114, wherein the proximal end of the housing is contiguous withthe distal end of the housing.
 129. The method of claim 113, wherein atleast a portion of the housing comprises an electrically insulatedmaterial.
 130. The method of claim 113, wherein at least a portion ofthe housing comprises an electrically nonconductive material.
 131. Themethod of claim 113, wherein the housing is substantially non planar.132. The method of claim 113, wherein the housing is substantiallyplanar.
 133. The method of claim 133, wherein the electrical circuit canprovide cardioversion-defibrillation for the patient's heart.
 134. Themethod of claim 133, wherein the electrical circuit can further providemultiphasic waveform cardiac pacing for the patient's heart.
 135. Themethod of claim 113, wherein the electrical circuit can providemultiphasic waveform cardiac pacing for the patient's heart.
 136. Themethod of claim 135, wherein the electrical circuit can provide biphasicwaveform cardiac pacing for the patient's heart.
 137. The method ofclaim 135, wherein the electrical circuit can provide triphasic waveformcardiac pacing for the patient's heart.
 138. The method of claim 113,wherein the electrical circuit can provide monophasic waveform cardiacpacing for the patient's heart.
 139. The method of claim 113, whereinthe electrode can emit an energy for shocking the patient's heart. 140.The method of claim 139, wherein the electrode can receive sensoryinformation.
 141. The method of claim 113, wherein the electrode canreceive sensory information.
 142. The method of claim 113, wherein atleast a portion of the electrode is non-planar.
 143. The method of claim113, wherein the single incision is made approximately at the level ofthe cardiac apex.
 144. The method of claim 113, wherein the singleincision is made approximately in the left anterior axillary line. 145.The method of claim 113, wherein the duckbill-shapedcardioverter-defibrillator is advanced proximate the patient's heart.146. The method of claim 113, wherein the duckbill-shapedcardioverter-defibrillator is advanced medially toward approximately apatient's left inframmary crease.
 147. The method of claim 113, whereinthe duckbill-shaped cardioverter-defibrillator is advanced proximate apatient's sternum.
 148. The method of claim 113, wherein theduckbill-shaped cardioverter-defibrillator is advanced approximatelybetween a patient's third and a patient's twelfth rib.
 149. The methodof claim 113, wherein the duckbill-shaped cardioverter-defibrillatorrefrains from directly contacting the patient's heart.
 150. The methodof claim 113, wherein the duckbill-shaped cardioverter-defibrillatorrefrains from directly contacting the patient's intrathoracic vessels.